JPH07199064A - Automatic focusing device for camera - Google Patents

Abstract

PURPOSE:To obtain an in-focus photography result even if a photographer performs shutter releasing operation during the movement of a subject by continuously driving a lens driving means without any stop even when exposure operation is started. CONSTITUTION:Once a defocusing quantity Dn is calculated, the driving means is driven by the quantity and at the end of the driving, storing operation is started. When it is decided that a body moves, the driving is performed uniformly at a constant speed throughout the period of storage calculation, and driving as to a driving quantity for correction accompanying the body movement. Namely, lens movement is performed even in the storage period, correction is required correspondingly, but easy since the movement in the storage period is constant in speed. Driving only for tracking needs not be so fast, so the influence on a time measurement error is small. Consequently, there is no restriction on exposure time for in-focus exposure, an in-focus photograph can be taken whenever the shutter is released, and the release responsiveness is superior.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing device such as a camera, and more particularly to a technique for identifying whether or not a target object is out of a focus detection field of view and driving the taking lens accordingly. is there.

[0002]

2. Description of the Related Art First, the structure of a conventional automatic focus detection device that does not perform tracking will be described with reference to FIG. The light emitted from the object a passes through the imaging optical system (photographing lens) L, and is guided via the quick return mirror M onto the finder screen S which is normally in a position conjugate with the film surface F. Also, a part of the light transmitted through the semi-transparent portion of the center of the quick return mirror M is reflected by the sub-mirror S. It is guided to the focus detection means via M. The focus detection means 101 has a known structure and is composed of a focus detection optical system, a charge storage type image sensor, a focus detection calculation unit and an image sensor drive control unit. Immediately after the end of charge accumulation, the defocus amount is intermittently calculated by the focus detection calculation unit. This defocus amount corresponds to the distance along the optical axis between the film conjugate surface, which is the predetermined image forming surface, and the image surface of the image forming optical system L.

The control means 102 receives data relating to the defocus amount from the focus detection means 101, drives the motor of the lens drive means 104, and moves the focus matching optical system included in the image forming optical system L to form a predetermined image. The surface and the image plane of the imaging optical system are controlled so as to coincide with each other. If the motor of the lens driving means is not capable of accurately controlling the driving amount by the input signal, the monitor means 10 configured by a photointerrupter or the like for detecting the movement amount of the focus matching optical system.
The control means 102 controls the drive of the focus matching optical system using the feedback pulse of No. 3. Of course, when the drive amount can be accurately controlled by an input signal like a pulse motor, the monitor means may detect the input pulse, or a means equivalent thereto may be used instead.

Generally, it is rather rare to move the entire image-forming optical system to perform automatic focus adjustment, but it is common to move a part of the image-forming optical system for focus adjustment to perform focus adjustment. . In this case, the amount of movement of the focusing optical system and the amount of movement of the image plane of the imaging optical system do not match. Therefore, in practice, a value relating to the ratio of the number of feedback pulses output from the monitor means 103 and the amount of movement of the image plane is recorded in the lens information generating means 105, and the control means 102 uses this ratio from the lens information generating means 105. Is read to calculate the required number of pulses corresponding to the required amount of image plane movement (defocus amount), and driving is performed until the feedback pulse reaches the required number of pulses.

However, this point is irrelevant to the essence of the present invention, and in the following description, the imaging optical system will be represented by a virtual single lens so that the essential points of the present invention can be easily understood. The following description will be given on the assumption that the moving amount of the image is equal to the moving amount of the image plane. Of course, even in the case of a single lens or the whole group extension lens, if the distance to the target object is extremely close, the above assumption does not hold at all. Therefore, in the case of a macro lens or the like, the value of the ratio is gradually changed according to the extension amount of the lens. It becomes necessary to switch the lens information generating means 105, and the function is required. However, here, regarding the value of the ratio, it is left to the lens information generating means. I will explain it using.

In FIG. 27, for convenience of explanation, the coordinates are fixed to such a virtual single lens L, and in that case the locus of the image plane of the object to be moved (solid line P) and the film plane are conjugated. The locus of the predetermined image plane (dotted line Q) is shown, and the horizontal axis represents time t and the vertical axis represents the distance between the image plane and the virtual single lens along the optical axis. The coordinates (t _n , x _n ) in the figure represent the charge accumulation start time t _n of the focus detection means 101 and the position x _n of the predetermined image plane at that time, and the coordinates (t _n ', x _n ').
Represents the accumulation end time t _n 'and the position x _n ' of the predetermined image plane at that time, and the coordinates (t _n ⁰ , x _n ⁰ ) are the focus detection calculation end time t _n ⁰ and the position of the predetermined image plane at that time. represents x _n ⁰ . Further, FIG. 27 shows a state of a focus matching operation in so-called intermittent driving, in which an object is moved to a ₁ ′, a ₂ ′, and a ₃ ′ with time, and the image plane is a ₁ , It shows a state of moving with a ₂ and a ₃ .

The image plane a of the object is obtained as the result of the first calculation.
₁And film side b₁Value D for the distance difference₁At time t
₁ ⁰When output from the focus detection means 101, the control means
102 is the defocus amount D as described above.₁The phase
While controlling the drive of the lens L to kill it,
Also object a₁′ Is a₂Since it is moving to ′, time t ₂
Lens on D₁Drive the lens and stop the lens drive
However, at the midpoint of the next accumulation time, the image plane is already a₂
Has been moved to, and the result of the second calculation is a₂And b
₂Value D of the position difference₂At time t₂ ⁰Focus on the hand
It is output from the stage 101. Then, the control means 102
Is the defocus amount D as described above.₂To offset
Control at time t₃Stop the lens drive to x
₃Even if the predetermined image plane is brought to the position of₂′
Is a₃Since it has moved to ′, it will not be in focus.

Thereafter, the same thing is repeated as shown in FIG. If the object did not move and there were no errors, it would have been possible to match the object image plane with the predetermined image plane in one accumulation / calculation / driving cycle. Even if the defocus amount includes an error of 10 to 20%, it should have been possible to make the object image plane and the predetermined image formation plane approximately coincident with each other in a few cycles.

However, when the object is moving in the optical axis direction as shown in FIG. 27, the distance between the object image plane a _n and the predetermined image plane b _n gradually increases in the first few cycles. However, the distance between the two is kept at a constant value determined by the moving speed of the object image plane and the responsiveness with the automatic focusing device, and the follow-up state continues without achieving focusing.

[0010]

In order to solve the follow-up state, the applicant of the present invention has proposed an automatic focusing device having an object tracking function in Japanese Patent Laid-Open No. 60-214325.
There, the image plane position at a predetermined time was obtained, and the image plane moving speed multiplied by the time term was added to this to calculate the target position, and the lens was driven toward this tracking locus and reached the locus. After that, the position of the image plane is chased every moment to drive along the locus.

In the example described here, the control relating to the release operation of the camera is not described. Since a general single-lens reflex camera has the arrangement shown in FIG. 1,
When the release operation is performed by the photographer and the mirror M and the sub-mirror SM bounce up, focus detection becomes impossible because no detection light flux reaches the focus detection means 101, and focus detection becomes impossible during mirror up.

Therefore, it is an object of the present invention to provide a method for obtaining a focused shooting result even when the photographer performs a release operation while the subject is moving.

[0013]

In the present invention, an image forming optical system L for forming a light image of a target object, an image forming surface on which the light image is formed, and a predetermined predetermined image forming surface (film Focus detection means 101 for outputting a defocus amount related to the distance in the optical axis direction of the imaging optical system from the conjugate plane), and lens driving means 10 for moving a focus matching optical system of the imaging optical system.
4. A correction member which receives a release member for instructing the start of mirror-up and exposure, and an output of the focus detection means, and which calculates an amount related to the movement of the image plane along with the movement of the target object in the optical axis direction. 100, the control means receives the calculation result of the correction means, controls the lens driving means so that the predetermined image plane moves following the movement of the image plane, and controls the lens drive means from the release member. Even when the release instruction is issued and the exposure operation is started, the control means has a control means for controlling the lens drive means so as to continuously drive the lens drive means without stopping before the exposure. Is characterized by.

Further, the control means receives the calculation result of the correction means and controls the lens driving means so that the predetermined image plane moves along the movement locus of the image plane of the target object. Even if a release instruction is issued from the release member and an exposure operation is started, the control means drives the lens so that the predetermined image forming surface moves along the movement locus of the target object image forming surface even during exposure. Control means (Fig. 22).

The main part of the present invention is explained in the seventh embodiment, and the solid line in the upper part of FIG. 22 and FIG. 23 shows the same contents as the solid line in the upper part of FIG. 12, and the high part indicates the mirror up period. Correspondingly, exposure is performed in the middle, and focus detection is impossible during this mirror up period. The low part is the mirror down period and focus detection is possible during this period.

[0016]

In the present invention, the condition for stopping the focus matching optical system before the exposure and performing the exposure with the optical system stopped before exposure is not established, and the focus matching optical system is continuously driven during the exposure. Further, it is in a driving state before and after the exposure, and preferably has an operation mode in which the driving state is maintained along the image plane locus at the image plane moving speed accompanying the movement of the object. Therefore, it is possible to cope with the timing change due to the mirror up at any time in the tracking operation sequence including the focus detection and the driving, and it is possible to take the photograph with the focus at any time regardless of the release operation by the photographer.

Further, since the driving state is maintained along the locus of the image plane even during the exposure, there is no restriction on the exposure time for the focused exposure, so that the release response is excellent.

[0018]

EXAMPLE A first example will be described. In this example, the lens drive is not performed at all during the accumulation / calculation, and the correction drive for tracking is collectively performed after the calculation is finished and before the accumulation is started, which is a drive method following the completely intermittent drive. The correction drive for canceling the movement of the object will be referred to as tracking drive. FIG. 1 is a block diagram showing the configuration of the first embodiment, and is the same as FIG. 26 used in the description of the conventional example except for the correcting means 100.

The correction means 100 receives the output of the focus detection means 101 and the output of the monitor means 103, determines whether or not there is an object movement, and when it is determined that there is an object movement, a correction drive for tracking the object. The amount is calculated, and on the basis of this, the control means drives the lens for tracking. FIG. 2 shows the state of tracking in the first embodiment, and uses the same expression method as in FIG. Here, Q indicates the state of driving by normal intermittent driving, and follows the locus P of the object image. Further, Q'shows the state of the tracking drive according to the first embodiment, and it is understood that the tracking is performed along the locus P and the near-focus state is always maintained. The difference between Q'and Q corresponds to the object movement correction amount calculated by the correction means.

Next, the processing contents of the correction means 100 will be described. Since the lens is not moved during the accumulation / calculation time, x ₁ = x ₁ '= x ₁ ^o , and the out-of-focus amount at time (t ₁ + t ₁ ') / 2 is the distance difference between point a ₁ and point b ₁ ( X _1-
x ₁ ^o ), and at the end of the calculation t ₁ ^o the focus detection means 10
The defocus amount calculated from ₁ is equal to this value D ₁ if there is no detection error. The n-th defocus amount calculated by the focus detection unit 100 will be represented by D _n .

The control means 102 uses the D ₁ calculated by the focus detection means 101 at time t ₁ ^o to drive the lens driving means 1
04 is controlled to count the number of feedback pulses of the monitor 103, and drive is performed until the image plane movement amount by the lens becomes equal to the defocus amount D ₁ . As described above, in reality, a certain amount of image plane movement ΔB related to the taking lens.
The amount of movement of the lens corresponding to f varies depending on the taking lens, and the number of feedback pulses Δn that gives the amount of movement of the lens often differs depending on the taking lens. Therefore, a conversion coefficient K _B for converting the image plane movement ΔBf into the feedback pulse number Δn according to the relationship of Δn = K _B * ΔBf is stored in the lens information generating means 105, and the actual drive control is performed using this.

This operation of converting the movement of the image plane into the number of feedback pulses is irrelevant to the essence of the present invention and therefore omitted for simplification, and all the following description will be expressed in terms of the amount of movement of the image plane. Immediately, the defocus amount D _{n as well as} the correction drive amount C _n described later are all described on the scale of the image plane movement amount. Now, the calculation end time t
It is desirable from the viewpoint of responsiveness that the driving from ₁ ^o to the accumulation start time t ₂ is as fast as possible. On the other hand, it is necessary to gradually reduce the speed between the stops, so the driving is high speed and non-uniform speed. In the tracking system of the previous application, charge accumulation was performed during this period, but the detected image was equivalently blurred due to the high driving speed.
Correction of defocus amount due to driving of non-constant velocity lens due to increase in position determination error due to slight detection error at each time of start of accumulation, speed change and end of accumulation and remarkably non-constant velocity near stop. However, there were some drawbacks such as not being able to be accurate. Therefore, in this embodiment, the accumulation is restarted at time t _{2 when the} high-speed and non-constant speed driving is almost converged. Time t ₂ ^o
The second defocus amount D ₂ is calculated at this time, which is a value (X ₂ −) corresponding to the difference between the point a ₂ and the point b ₂ which is the out-of-focus amount in the middle of the accumulation time t _{2 to} t ₂ ′. x ₂ ^o ), except for error. If the object is not moving and the detection error is sufficiently small, D ₂ should be a very small value compared to D ₁ , so in principle it can be determined from the value of this ratio whether or not the object has moved. . Actually, in the follow-up state such as the locus of Q for n ≧ 3 shown in the conventional example of FIG. 27, the calculated defocus amount D _{n of} each time does not converge to zero forever and becomes a substantially constant value, and D _n / D It can be seen that _n-1 ≈1. However, when additional correction drive is performed in addition to the drive based on the normal defocus amount as indicated by Q ′ in FIG. 2, the above-described identification is performed using the calculated defocus amount D _n itself. Becomes impossible.

Therefore, as shown in FIG. 3, a correction shortage amount calculation means 100a is provided in the correction means 100 to calculate a quantity P _n given by the equation as a quantity representing the shortage of convergence, and this is the basis. . P _n = D _n + those [previous drive amount] -D _n-1 ...... where expression of n-th defocus amount D time _n is calculated t _n ^o Currently, D _n is the focus detection unit 101 The latest defocus amount D _n−1 calculated by the above is the previous defocus amount. [Previous driving amount] is time t ^o
_n-1 ~t actually driven value X between the _n (n-1) or time t ^o Examples _n-1 calculated results in X (n-
The calculated value D _n-1 ′ which is the basis for driving only 1). Of course, both are equal when there is no error (D _n ′ = X (n)).

Now, _assuming that the correction drive amount for tracking is C _n , the drive amount D _n ′ is as follows: D _n ′ = D _n + C _n .. Can also be expressed as P _n = D _n + C _n-1 ... '' As can be seen from FIG. 2 according to the definition of the above equation, n ≧
After 3, the convergence deficiency amount P _n is the point a _n and the point a _n-1.
The difference in the distances (for example, P ₄ = D ₄ + C ₃ ) is nothing but the driving amount of the object image.

The time t _{1 at which the first} calculation result is obtained
Since there is no previous result at the time of ^o , P ₀ is set to a sufficiently large value as an initial condition, for example, about 1000 〓, and P ₁ =
Decide to be D ₁ . Therefore, in this case, P ₁ does not correspond to the amount of movement of the object and becomes P ₁ / P ₀ 〓 <〓1. Therefore, an object movement determination means 100b is provided in the correction means 100 as shown in FIG. 3 to determine the presence or absence of object movement.

Next, a specific example of the object movement determining means will be described. Table 1 shows changes in the convergence deficiency amount P _n as a result of performing tracking drive of a moving object as shown in Q ′ of FIG. 2 in accordance with a routine described later on the assumption that a detection error exists to some extent.

[0027]

[Table 1]

In this example, the first convergence deficiency amount P ₁ is 10 〓
When n = 2,3, _Pn converges rapidly, but it does not reach below the allowable focus range of 〓05 to 〓15〓, and when n = 4 to 7, the value of _Pn is It is constant around 4〓. Immediately, even after n = 3 to 4, the value of P _n does not converge within the permissible focus range and becomes a substantially constant value, which indicates the movement of the object, and the value of P _n at that time is the object in one cycle. It corresponds to the movement of the image plane accompanying the movement.

From this fact, P _n is 5 ≦ P _n / P _n-1 <2
It is possible to determine that the object is moving by entering the range of the degree. If the object is stationary, the current defocus amount is generally 20% or less of the previous defocus amount. Practically, the object movement determination means compares the magnitude of P _n / P _n-1 with a predetermined constant (threshold value) k to determine whether or not the object is moving. Considering the influence of various errors, the practical value range of k is 〓3 ≤ k ≤ 〓8, and 〓4 ≤ k ≤ 〓6 is considered optimal. And P _n
When / P _n-1 ≧ k, the object movement determination means 100b determines that there is an object movement. Further, it can be seen that the image plane movement corresponding to the object movement in one cycle at this time is given by approximately P _n . Therefore, the correction means 100 is further provided with an object movement correction amount calculation means 100c to calculate the correction drive amount C _n for tracking. That is, when the object movement determination means determines that there is object movement, C _n = P _n when there is no object movement, C _n = 0.

Next, FIG. 4 conceptually showing the flow of processing.
A description will be given with reference to the flowchart of FIG. 4A and the flowchart of FIG. 4B which specifically shows the processing contents of the first embodiment. First, in step (1), the above-mentioned initial value setting is performed. The accumulation starts in step (2) and the accumulation ends in step (3), and the image output of the charge accumulation type image sensor of the focus detection means is sent to the focus detection calculation unit in the focus detection means. Then, in step (4), the focus detection calculation is started, and in step (5) the calculation is completed, and the defocus amount D
_n is calculated. When the defocus amount D _n is output from the focus detection means in this way, the control means 102 is normally used.
Drives the lens based on this data. However, in this embodiment, the defocus amount D _n is first subjected to the tracking drive processing by the correction means 100.

The step (6) corresponds to the convergence shortage amount calculation means 100a in the correction means 100 and calculates the convergence shortage amount P _n . Step (7) corresponds to the object movement determination means 100b. In step (7) of FIG. 4B, if 〓P _n 〓> k * 〓P _n-1 〓, the object is moving. To be judged. Step (8) corresponds to the object movement correction amount calculation means 100c, and calculates the correction amount C _n according to the presence or absence of the object movement. Next, in step (9), the drive amount D _n ′ is calculated. This D _n ′ is converted into the image plane movement amount as described above, and the control means 102 determines the correspondence relationship between the value of this D _n and the feedback pulse from the monitor means 103 as described above. The drive control is performed in association with the conversion coefficient K _B stored in 105.

Next, in step (10b), the value required for the next calculation is stored, driving is started in step (11b), and driving is continued until the driving stop condition in step (12b) is satisfied. When the stop condition is satisfied, the process returns to step (2) and the accumulation is restarted. As described above, the first embodiment is an intermittent driving method in which charge accumulation, calculation, and driving are sequentially performed without overlapping even when tracking is performed. Therefore, as described in step (9) as D _n ′ = D _n + C _n , the drive amount D _n ′ is the defocus amount D.
It is given as the sum of _n and the correction drive amount C _n for tracking. If the drive amount calculated in step (9b) is completely achieved by executing the drive in steps (11b) and (12b), there is no problem, but there is a difference between the calculated drive amount and the actual drive amount. When it occurs, step (6
The calculation of the convergence deficit amount P _{n in} b) is incomplete in the equation, and it is necessary to use the equation. In this case, the value of the previous drive amount in the equation must be a value obtained by back-calculating the amount X (n-1) actually driven last time from the accumulation of the feedback pulses, not Dn _-1 'calculated last time.

As described above, according to the first embodiment, the intermittent driving is completely followed, and therefore the lens is stopped during the accumulation time. Therefore, it is calculated as in the case of JP-A-60-214325. The accuracy of the defocus amount does not deteriorate,
The presence or absence of the object movement can be accurately determined, and an accurate tracking drive can be achieved. Further, in the case of the conventional tracking method of Japanese Patent Laid-Open No. 60-214325, since it is premised that the driving is performed in parallel during the accumulation time and the calculation time, the microcomputer becomes multitasking, and the event counter and timer are However, if a microcomputer with a limited number of CPUs is used, the programming becomes difficult and quick processing cannot be performed.

However, the tracking software of this embodiment does not become a multitask because it is an intermittent drive, and the tracking drive is sufficiently effective without monitoring the time at all, so that the program can be easily constructed. At the same time, there is an advantage that the capability of the microcomputer currently running the drive software can be sufficient. Also, the amount of software actually added is
Since the tracking drive can be performed by adding the small number of calculation steps shown in FIGS. 4A and 4B to the conventional intermittent drive software, the compatibility with the conventional software is very excellent.

Next, a second embodiment in which the processing of the object movement discriminating means 100b described in the first embodiment is made more accurate will be described. The correction drive amount C _n when the object is moved does not necessarily have to be set strictly as described above, and for example, the convergence shortage amount P _n may be multiplied by a certain coefficient close to 1, In the drive control of 1), the coefficient is set to 1 or less (0.9, 0.8, ...) in the case of overrun, and the coefficient is 1 or more (1.1, 1.
2, ...) may be set. [Second Embodiment] As described in the first embodiment, when the object movement determination means determines that there is object movement, intermittent driving (tracking drive) including tracking correction is performed and it is determined that there is no object movement. In this case, normal intermittent drive (convergence drive) is performed. However, if the determination accuracy of the object movement determination means is not sufficient and it is erroneously determined that there is an object movement when there is no object movement, there is a problem that the driving operation tends to be hunting. A method for preventing erroneous determination in order to solve this problem will be described with reference to FIG. The flowchart of FIG. 5 replaces step (7) described in the first embodiment, and here, in step (1001), the current convergence shortage amount P _n and the previous convergence shortage amount P _n-1 have the same sign. Whether or not the object is moving is determined by checking whether or not it is present. If the code is not the same, it is determined that the object is not moving. If the code is the same, the next judgment step (1002) is performed. It surely determines whether the object is moving. Sokuwachi step (1001), 2 of which determines the presence or absence of an object moving step, 〓P _n ¬> k * 〓P _n-1 P _n and P _n be satisfied 〓 is (1002) _This is because it is determined that the object is moving when _-1 has a different sign. It should be noted that the conditions of steps (1001) and (1002) are collectively P _n / P
The determination of _n-1 > k may be used.

Next, consider the case where the object suddenly deviates from the focus detection visual field. In this case step (100
When the condition of 2) is met (for example, P _n / P
_{If n−1} ≧ 4), the lens is driven with the defocus amount based on P _n , so that there is a problem that a significant overrun occurs. What was provided to solve this problem was 〓P _n 〓 <in step (1003).
Judging by r * 〓P _n-1 〓, r is a constant of about 2≤r≤3. Immediately, _if 〓 P _n 〓 becomes significantly larger than 〓 _{P n-1} 〓, that is, if step (1003) is negative, it is determined that the object is out of the detection field of view, and it is erroneously determined that the object has moved It is assumed that the determination is prevented and normal intermittent drive (convergence drive) without tracking correction is performed.

Next, step (1004) will be described. The purpose is to increase the relative ratio of the defocus amount detection error included in the convergence deficit amount P _n when there is no object movement in the vicinity of the in-focus state or if there is little object movement, regardless of whether or not there is an object movement. This is to eliminate the possibility that the determination of 1002) is influenced by the influence of the detection error, and to prevent the drive from becoming hunting due to the wrinkles between the convergences when there is no object movement. To achieve this purpose, the allowable width δ _a
Is provided, it is determined that there is no object movement unless _{P n} 〓> δ _a . Here, the magnitude of δ _a is determined as a value that reflects the defocus amount calculation error and the depth of field, but is generally a value of about 05 to 2 〓. That is, when the lens is close to the in-focus position and P _n is in a range that can be regarded as being generally in the in-focus position, only convergent drive that is not tracking drive is performed. By this step, the movement cannot be detected when the movement of the object is small, but in this case, there is no problem because the normal intermittent drive (converging drive) without tracking does not significantly follow. Further, this step (1004) is not limited to this position and may be performed before step (1001).

As described above, according to the second embodiment, the determination of the movement of the object becomes more complete, so that the problem of hunting during the normal operation accompanying the addition of the tracking software is eliminated, and the stable operation is guaranteed. Also, in the second embodiment, since the time is not measured as in the first embodiment, it can be dealt with by a very simple software process. Third Embodiment Up to now, the timing determined only by the operating characteristics of the focus detection means and the lens drive means has been discussed, but when considering the camera, it is necessary to consider the timing of exposure. The drive described in the first and second embodiments is intermittent drive, and the drive itself has a stepwise shape. On the other hand, since the movement of the object changes to Nameraca, it is preferable that the exposure timing be set appropriately. In other words, even if the tracking drive is stepwise because the tracking drive is intermittent drive, if the exposure timing is properly adjusted, it will be possible to obtain a perfectly focused photograph taken. Become. How to set the timing of such exposure will be described in a third embodiment below. The tracking method in the third embodiment is the same as in the first and second embodiments.
The example is assumed. Regarding the shutter release, there are an independent mode that allows exposure (mirror up) regardless of whether focus detection is performed by the focus detection system, and a focus priority mode that allows exposure when focus determination is made. However, we will focus on focus priority mode here.

Before starting the detailed description of the third embodiment, how to set the exposure timing in the known normal intermittent drive system will be described with reference to FIG. When the defocus amount is calculated in step (5), the magnitude of the defocus amount calculated in step (81) is compared with a predetermined focusing range δ, and the magnitude of the defocus amount is larger than δ. Then, when the lens is driven in step (82), and it is determined in step (83) that the driving of the predetermined driving amount is completed, the next charge accumulation is started. This cycle is 1-3
When it is found that the defocus amount is smaller than δ in the determination in step (81) after the process is repeated, the process proceeds to step (84) to perform the focusing process. The focus process here means to permit lighting of the focus display and mirror up for exposure of the film, and if the shutter is released before this time, exposure is not performed until this point. Instead, mirror exposure and exposure are performed in response to the exposure permission signal. This is the essence of the focus priority mode. In a normal case where there is no movement of the object, this process does not cause any particular problem. However, when the object is moving, there is a disadvantage that the above-mentioned normal processing causes exposure at an out-of-focus position. This will be described with reference to FIG. In the example of FIG. 7, since the image locus P passes through the midpoint of the charge accumulation time Tint, the defocus amount D _n calculated at the end of the calculation t _n ^o is “D _n 〓”.
<Δ, and the focus processing routine of step (84) in FIG. 6 is entered. If t _n ^o previously exposure enabling if the shutter release is if taking place at the time of t _n ^o according to step (84) (mirror-up permission) is generated, the delay time the mirror-up conducted in accompanying mirror-up Tup The exposure of the film occurs at a later time t _expo . However, at this point in time, as is clear from the figure, the locus P of the image has been separated, so an out-of-focus photograph will be taken. That is, 〓D _n 〓 <δ only means focusing at the time of the midpoint of the charge accumulation time, and the image plane is deviated by the delay time from this moment to the exposure.

In order to solve this drawback, in the third embodiment, as shown in FIG. 8, a focusing process performing means 100d is provided in the correcting means 100, and an optimal focusing process is performed during tracking drive. To do so. This operation is shown in Figure 9.
Corresponding to step (10). (Step (1) ~
((9) is the same as FIG. 4 (a)) Next, at this step (10)
Will be described with reference to the flowcharts of FIGS.

In step (1101) of FIG. 10, whether or not there is an object movement is determined according to the result of step (7). If there is no object movement, steps (81), (8)
2) Go to (83) or (84). Since this corresponds to the same number in FIG. 6, its explanation is omitted. When it is determined that the object has moved in step (1101), driving is started in step (1102), and step (1103)
If the predetermined driving stop condition 〓 is satisfied in step (110)
Going to 4), the focusing process 〓 is performed. Step (11
The contents of the focusing process 〓 of 04) are the same as the contents of the focusing process 〓 of step (84), and the exposure is permitted and the display is turned on. However, in this case, since the object is moving, the display is turned off after a predetermined time elapses. Is good.

The reason why a photograph in focus can be taken even if there is an object movement by doing so will be described with reference to FIG. According to the tracking driving method in the first and second embodiments, the tracking is controlled so that the loci of P and Q'substantially intersect at the moment regarding the midpoint of the charge accumulation time Tint during tracking.

Therefore, if the cycle time is the same, the next intersection of P and Q'will occur after the end of driving Tin.
Expected to be t / 2 later. On the other hand, the delay from the start of mirror up to the exposure is Tup, and the time difference between them is δ
If T, then δT = Tup−Tint / 2. Therefore, if the mirror is moved up by .delta.T prior to the timing at which it is decided to instruct the resumption of the storage after the driving is completed, the exposure can be made to be substantially near the intersection of P and Q '.

By the way, in the case of a camera body of Tup≈50 msec, Tint / 2 changes depending on the lightness and darkness of the object, but 0 to 50 msec in most cases except when it is very dark.
Therefore, 0 ≦ δT ≦ 50 m sec, and 20 to 30
Mirror up should be performed earlier than the timing at which accumulation is scheduled to resume for m sec. As a first example of how to set the timing, it takes about 20 msec from applying the brake to stop the lens drive to completely stopping it, and apply the brake when the image surface moves about 50 μ in the meantime. The mirror-up timing can be matched with the timing, and the storage restart timing can be set 20 to 30 msec later. As a second example of how to set the timing, if it takes 20 to 30 msec for the remaining drive amount to be reduced from 150 μ to 50 μ in terms of image plane movement, the mirror-up timing is set to 50 μ when the remaining 150 μ remains. The purpose can also be achieved by setting the timing of braking and resuming storage at the remaining time.

Of these, the case of the second example will be described with reference to FIG. When there is an object movement, the step (120
The lens drive is started from step 1) to step (1202). It is assumed that the values of δ _P and δ ₀ are set so that the time until the remaining drive amount changes from δ _P to δ ₀ with respect to the movement of the image plane is approximately δT. When the remaining drive amount becomes δ _P or less with respect to the image plane movement in step (1203), step (12
Proceeding to 04), focusing processing including mirror up permission is performed. Of course, if the shutter release is not done up to this point, the mirror-up will not be executed even if the mirror-up permission is issued. The drive proceeds further and step (120
If the drive stop condition of 5) is satisfied, that is, if the image plane movement amount corresponding to the remaining drive amount becomes δ ₀ or less, step (1206)
The brake is applied at the step (120
In 7), it is confirmed that the main mirror is in the mirror-down state. When the main-mirror is in the mirror-down state, the procedure returns to step (2) in FIG. 9 to resume the accumulation. If the shutter button is in the release state in advance and the mirror-up permission is received in step (1204) and the mirror-up is actually performed, it is determined in step (1207) that the mirror-down state is not established, so the exposure ends. The process stops at step (1207) until the state returns to the mirror down state, and when the mirror goes down, the process moves to step (1204) in FIG. 11 to resume the accumulation.

By the way, the value δ _P in step (1203) may be set to a constant value, but the charge accumulation time is monitored and δT corresponding to it is calculated, and the value of δ _P is set according to the value of δT. Perfect to change. Although the case where δT> 0 has been described above, δT may be obtained depending on conditions.
It may occur when <0. However, in this case, since the mirror up timing is delayed from the drive end timing, δ is set from the drive end timing.
It is easy because it only has to count and delay T time.

Although the method of compensating for the error of δT has been described strictly in the above description, the focusing process (mirror up permission) is performed when δT is almost 20 to 30 sec. Even if the timing of the storage resumption instruction is not intentionally shifted, a substantially problem-free result can be obtained. Next, a case where it is determined that there is no object movement in step (1201) will be described. The magnitude of this case 〓D _n '¬ and [delta] _f in step (1210) are compared. For reference, since there is no tracking in this loop, it is equal to D _n ′ = D _n . Here, δ _f represents the width on one side of the focusing zone and is 50 to 200 μ.
It is a measure of size. If “D _n ′”> δf, the identification flag 〓 is set to 0 in step (1211), and driving is started in step (1212). Next, in step (1213), the step (12
The brake is applied in 14), the step (1207) is passed, and the accumulation is restarted in step (2). 〓D _n '¬ <[delta] returns to again step in this manner (1210)
_When it becomes _f , it proceeds to step (1215). In step (1215), focusing processing such as display lighting and mirror up permission is performed. Next, at step (1216), 1 is added to the identification flag 〓 and the fact that the focus zone is entered is stored. In step (1217), 〓D _n '¬ <δ _c (0 <δ _c
It is checked whether <δ _f ) or 〓 ≠ 0, and if this condition is satisfied, drive is not performed and the next accumulation is started.

Here, δ _c is a value of about 0 to 50 μ,
This is a shiki value provided to stop the lens near the center of the focusing zone. If the condition is not satisfied in step (1217), that is, 〓 = 0 and δ _f > 〓D _n ′ 〓> δ _c
In this case, the driving is started in step (1212), the driving is continued until the driving stop condition driving remaining amount <δ _c, and then the braking is applied in step (1214).

The main points of the above third embodiment can be summarized as follows. That is, the in-focus defocusing means has at least a predetermined value (50 .mu.
If the object is not moved when there is no object movement, the focusing process is performed after or near the end of the tracking drive. To destroy.

Thus, in the third embodiment, by changing the timing of the focusing process, that is, the turning on of the focusing display and the generation of the mirror-up permission, with and without the tracking drive,
Even if there is a tracking operation, the exposure can be performed at the most effective moment, and even if the tracking is performed by intermittent drive, a photograph that is perfectly focused on a moving object is taken. It becomes possible.

In the third embodiment, the time measurement is not always necessary, and even if it is used, it is the value of the charge storage time.
Since this value is indispensable when controlling the accumulation time by software even in a normal focus detection device without tracking, it is often measured, and it can be diverted. Since the load does not increase and the drive is intermittent, there is no change.
It does not become multitasking as in the case of 0-214325, and the feature of ease of software creation described in the first embodiment is not lost. [Fourth Embodiment] In the above third embodiment, how to set the exposure timing has been described. However, it should be noted that the above description applies only to the timing of the first exposure, and the timings of the second and subsequent exposures during continuous shooting are also different. That is, until the first exposure, this operation is repeated with (accumulation / calculation / driving) as one cycle. Therefore, it suffices to set the exposure timing based on such a premise. Then, it suffices to consider the coincidence of the timing between the moment of the first exposure and the moment of giving the midpoint of the planned accumulation time.

However, for the second and subsequent times in the continuous shooting mode, (storage / calculation / driving / mirror up period) is set to 1
It is necessary to consider a cycled repeating operation, and the exposure moment exists in the center of the mirror-up period, so it is impossible to match the central time of the accumulation time with the exposure moment. A tracking method in such a case will be described as a fourth embodiment below. Also in this case, the basic tracking operation is based on the first and second embodiments. The upper diagram of FIG. 12 shows the timing of each operation during continuous shooting by a motor drive. The cycle of continuous shooting is T,
The period during which the main mirror is raised is T _M. The mirror up period T _M is the delay time Tup associated with the mirror ascent, the exposure time Ts and the delay time Tdown associated with the mirror lowering.
Composed of. The period T _W indicated by the broken line in the figure corresponds to the period during film winding after exposure. The time from the end of winding or the end of calculation to the start of mirror up is T
_{At D} , the lens is driven during this time. As described above, the mirror-up start timing is set when the remaining drive amount becomes a constant amount (for example, 50 μ or 150 μ) converted into the image plane movement amount.

In the case of the configuration of FIG. 1, focus detection cannot be performed when the mirror is raised, so that accumulation is started at the same time as the mirror goes down, and as shown in FIG.
The defocus amount is determined when int and the calculation time Tcal have passed. When the lens driving is prohibited during the film winding, even if the defocus amount is calculated, the lens driving is delayed until the winding is completed.

Under the continuous shooting condition after the end of the first exposure in such an operation mode, δT ₁ = between the timing of the exposure and the timing of the central point of the integration time.
There is a time difference of Tdown + Tint / 2. By the way, as described above, according to the tracking driving method described in the first embodiment, as shown in FIG. 12, P and Q ′ are corrected driving for tracking such that they intersect at the midpoint of the accumulation time. Is being done. However, as it is, the driving is intermittent, so at the exposure timing, a photograph out of focus can be taken by the amount Δ that the object image plane has moved during δT ₁ .

The fourth embodiment considers the out-of-focus Δ based on the shift δT ₁ between the exposure timing and the midpoint of the accumulation time, and corrects it as the convergence excess / deficiency amount. As shown in FIG. 14, 100e is provided in the correction means 100 so that when a moving object is continuously shot, a focused photograph is taken while tracking the moving object. That is, the correction drive amount for tracking is Δ
As shown in FIG. 13, the tracking drive is controlled so that P and Q'overlap at the timing of exposure by reducing the amount.

Next, a method of calculating Δ will be described. FIG.
Since it is given by Δ = P _n * δT ₁ / T, it can be accurately determined by counting the cycle time T and the accumulation time T int. However, since the range of values that can normally be taken by both δT ₁ and T is limited, α (= δT
_{If 1} / T) is used as an appropriate constant and Δ = P _n * α is calculated, a large error does not occur. In this case, there is an advantage that it is not necessary to count δT ₁ and T.

The value of the above-mentioned constant α is in the range of 〓1≤α≤〓5 and often becomes a value of about 〓2. Further, in reality, the locus of the object image plane indicated by P in FIG. 13 does not become a straight line, and the inclination increases with time when the object approaches, and the inclination decreases with time when the object moves away. Therefore, it is preferable to determine the moving direction of the object by the sign of P _n and change the value of α by this. That is, _let α be α when the object is moving away and α _n when it is approaching α
_{Make f} > α _n . By doing so, the value of Δ becomes large when the object moves away, and the correction drive amount for tracking decreases, which can be matched with the decrease in the inclination of the object trajectory.

Next, the correction procedure will be specifically described with reference to FIGS. FIG. 15 is a flowchart showing a schematic flow. Between the steps (8) and (9) of FIG. 9, a step (8) ′ of calculating and correcting the convergence excess / deficiency amount Δ as the convergence excess / deficiency amount correction means 100e is performed. include. FIG. 16 shows more specifically the part from step (6) to step (10).

Steps (6), (7) and (8) are the first and second steps.
This is as described in detail in the examples. Step (81) (8
2) and (83) correspond to step (8) 'in FIG. 15. First, in step (81), it is checked whether or not the continuous exposure is being performed and the first exposure has already been completed. In other words, it is checked whether or not there is a mirror up / down operation between the final lens driving operation and the current accumulation operation cycle. That is, since the first exposure is performed at the timing according to the third embodiment, the convergence excess / deficiency Δ is not corrected, and therefore the process immediately proceeds to step (9). During continuous shooting, the above-mentioned convergence excess / deficiency amount Δ is calculated in step (82), and the above-mentioned Δ is added to the tracking correction drive amount C _n in step (83).
The corrected drive amount C _n is calculated by further correcting
Move to next step (9). The subsequent steps are the same as those already described, and will be omitted.

As described above, according to the fourth embodiment, it is possible to correct the movement of the object image plane corresponding to the time difference between the exposure instant and the time which gives the midpoint of the accumulation time. On the other hand, a focused photograph is taken. Also in this embodiment, basically, since the CPU is intermittently driven, the CPU hardly needs to perform multitask such as parallel processing of accumulation calculation and driving, and software construction is easy.

As described in the third and fourth embodiments,
Optimal control conditions differ between the first exposure and the second and subsequent exposures during continuous shooting by a motor drive. Therefore, the correction means needs to identify this point and perform optimal control. [Fifth Embodiment] As described above, the focus priority mode is assumed in the third and fourth embodiments. That is, even if the shutter release is performed, the mirror-up is not performed until the exposure detection signal is output from the focus detection system. That is, the mirror-up permission signal is output at the end of the tracking drive or just before the end of the tracking drive, and the mirror-up is performed accordingly.

However, this has the drawback that a photograph at the intended moment cannot always be taken. Therefore, an independent mode in which the mirror is raised and the exposure is performed at the moment when the shutter release button is pressed even if the focusing condition is slightly loosened may be considered. In the fifth embodiment, the conditions for enabling the in-focus photography as much as possible in such an independent mode will be described.

In the motor drive of a single-lens reflex camera, the maximum speed may be about 5 frames / second. Timing in such a case will be described with reference to the upper diagram of FIG. The continuous shooting cycle time T is 200 msec. Of these, the exposure time is 20 msec when the mirror-up time Tup is 50 msec, and the remaining time is when the film winding time T _w that starts after the exposure is 100 msec. T _D is only about 30 msec.

If the time from when the brake is applied to when the brake is stopped is expected to be 10 to 20 msec, the net drive time is 10 to 20 msec, and the lens cannot be actually driven. Therefore, in order to match the focusing operation to the motor drive as fast as possible,
It is preferable to allow the lens to be driven during the period Tup from the raising of the mirror to immediately before the exposure. If Tup 50m
If there is sec, the time that can be used to drive the lens is T _D + T
Since it comes up in about 80 msec, the drive amount required for tracking can be covered in most cases. Therefore, it is important to drive the lens even during the Tup period in order to provide the fastest possible response.

The fact that the focus detection system and the exposure timing have a predetermined relationship in the focus priority mode is
Although it is clear from that premise, even in the case of the independent mode in which exposure is performed in response to the shutter release button being pressed regardless of the state of the focus detection system, the focus detection system actually operates between the operation timing and the exposure timing. Has a certain relationship with each other. As a result, even in the independent mode, it is possible to control so that the focus state becomes almost good at the moment of exposure. That is, the above-mentioned certain relationship is inevitably generated by providing a condition that charge accumulation is started at the same time when the main mirror is fully lowered. By conditioning in this way, the same parameter δT _{1 as} described in the fourth embodiment has meaning. That is, when mirror up / down occurs between the final lens driving operation and the current accumulation / calculation cycle, the time difference from the exposure time to the intermediate time of the current accumulation time is δT ₁ .
From this point of view, it can be seen that the same processing as that described in the fourth embodiment is effective in the fifth embodiment except that the lens driving time largely falls within Tup.
Then, the influence of the fact that the lens driving time is largely interrupted in Tup will be described below.

First, letting ΔZ ₁ be the amount of image plane movement that can be made by lens drive during the time during which the lens can be driven between frames.
When the moving speed of the object image plane is 5 frames / second, 5
It is possible to track a moving object equivalent to × ΔZ ₁ / sec. In order to increase this capability, it is necessary to increase the driving power so as to satisfy the above relationship. FIG. 17Q 'shows just an example in the case of such a critical condition, in which the brake is applied immediately before the exposure to stop. Also, when the above critical condition is slightly exceeded, the lens may move during exposure as in Q ″, but in such a case the image plane is moving much faster in the first place.
There is no point in stopping the lens strictly, and there is no problem even if it moves a little. Furthermore, when the object movement is large enough to exceed the critical condition, the tracking cannot avoid being followed.

As described above, according to the fifth embodiment, by allowing the lens drive even after the mirror is raised, the independent mode,
Even in the case of a high-speed motor drive, it is possible to perform in-focus shooting. Also in this case, the convergence excess / deficiency correction unit 100e determines Δ in the same manner as described in the fourth embodiment and corrects the convergence excess / deficiency. Of course, also in the focus priority mode of the fourth embodiment, it is possible to positively drive the lens during the Tup period and increase the responsiveness by increasing the value of δ _P. [Sixth Embodiment] In the above embodiments, the tracking drive method is not necessarily required to measure the time, and can be replaced with the representative value even when necessary. Moreover, the case where the accumulation time and the calculation time are almost the same every time was considered. Since the same object is actually being tracked during tracking, the above conditions are almost satisfied. Also, according to the simulation, even if there is some variation, it will be overrun or underrun each time by that amount, but as a whole it was found that sufficiently effective tracking drive is performed compared to normal intermittent drive. is doing.

However, it is possible to eliminate the above-mentioned slight overruns and underruns by constructing the tracking software in consideration of the variation in the time intervals. In the sixth embodiment below, such a case will be described. To do. Although the object movement correction amount P _n for one cycle is directly used for the calculation in the above-described embodiments, in the present embodiment, the object movement is performed by measuring the time T (n-1) during this period as shown in FIG. The speed corresponding to the above is calculated, and as a result, the correction insufficient amount sequential correction means 100f included in the correction means 100 of FIG. 19 is calculated.
Is to finely correct the tracking drive,
No driving is performed during the accumulation calculation, and the driving is essentially intermittent.

The flow of processing will be described with reference to the flowchart of FIG. Steps (1) to (5) are the same as before. In the next step (55), the drive amount X is calculated from the event counter value Event or the register value Regis.
Calculate (n-1). Here, the event counter stores the counting result of the feedback pulse relating to the previous drive from the monitor means.

In step (6), the convergence shortage amount calculation means 10
0a is the convergence shortage amount P _{n according} to the formula P _n = D _n + X (n
-1) -Dn _-1 is calculated. In step (1), the object movement determination means 100b determines whether or not an object has moved.
The specific method is as described in the first and second embodiments. If there is an object movement, the process proceeds to step (31) and the flag IDO
= 1. Steps (32) and (33) correspond to the contents of the object movement correction calculating means 100c in this embodiment. In step (32), the amount corresponding to the difference between P and Q'in FIG. The _{C n = P n * {Tint} (n) / 2 + Tcalc (n)} / T (n-1) ......... step (33) is a process corresponding to that described in the third embodiment and the fourth embodiment In order to optimize the exposure timing, the correction of P _n * δT / T (n-1) ... Is further performed. Here, δT is an amount that depends on the exposure timing.

In step (34), the driving amount D _n ′ is obtained as the sum of the defocus amount D _n and the tracking driving amount C _n . Now, the lens driving start is automatically started by setting the number of pulses corresponding to the driving amount in the register Regis, and the feedback pulse output from the monitor means 103 is counted by the event counter and the event counter is started. It is assumed that an interrupt (EVC interrupt) is generated at the time when the accumulated value of (1) becomes equal to the value set in the register Regis. Here, a separate flag is set for the driving direction, and the rotation direction of the lens drive motor is controlled by this flag, but the description is omitted in the flowchart.

In step (35), the event counter value Event is reset to 0, and the register Regis (〓
Sets the number of pulses corresponding to D _n '¬-δ _c). This automatically starts the lens drive. Then, in step (36), the EVC interrupt is enabled and the stop interrupt is awaited. The step (37) corresponds to the correction deficiency amount sequential correction means 100f in FIG. 19, and since the correction amount calculated in the step (32) is the one at the end of the calculation, the correction amount after the end of the calculation is sequentially corrected. To do.

That is, since the amount of movement of the object image plane is given by the following expression ΔP _n = P _n * ΔT / T (n-1) ... During the time ΔT, it corresponds to ΔP _n 〓 every ΔT seconds. The number of pulses is added to or subtracted from the register. Whether or not the addition is performed is determined by the relationship between the driving direction initially determined and the moving direction of the object image plane, that is, the sign relationship between D _n ′ and P _n . Here, if ΔT is set to about 1/10 or less of the accumulation time, it can be considered that the constant speed driving is substantially performed during the accumulation. In this way, the lens is driven by the broken line R in FIG.
, The event counter value Event and the register value Regis become equal at the time when Q ′ and R intersect, and an EVC interrupt is generated. EV in step (38)
The C interrupt is set to disabled, and in step (39), the lens drive is stopped by applying a short brake, and at the same time, the addition of ΔP _{n to} the register is also stopped.

In step (40), it is identified whether or not there is an object movement, and if there is, in step (41), focusing processing such as mirror up permission and focusing display for a predetermined time is turned on.
I do. In step (42), the amount required for the next calculation,
P _n , D _n, etc. are stored and n = n + 1. Step (4
In step 3), if the mirror is down, proceed to step (2)
If the mirror is up, wait until the mirror is down and return to step (2).

On the other hand, if it is determined in step (7) that the object has not moved, the normal processing routine after step (45) is entered. Step (45) a flag indicating that there is no object movement in, it adopts a defocus amount D _n as the drive amount D _n 'in step (46). Step (4
In 7), the magnitude of 〓 D _n ′ 〓 and δ _c is determined and 〓 D _n ′ 〓 ≦
If δ _c , in step (51), the focusing process 〓, that is, focusing display lighting and mirror up permission are performed. Then step (5
In step 2), jump to step (42). In step (40)
When D _n ′ 〓> δ _c, the focus indicator is turned off in step (48), it is turned off, the driving is started in step (49), the EVC interrupt is permitted in step (50), and the driving is finished. Wait for

As described above, according to the present embodiment, even if the accumulation time, the calculation time, the winding time, the drive time, etc., fluctuate to some extent, the required drive amount for tracking is changed according to the passage of time. Therefore, it is always possible to shoot in focus.
The three-dot chain line S in FIG. 18 is an exaggerated illustration of the case where the start of the lens driving is delayed due to the long winding, but the lens is driven until it intersects with the target broken line R, and thus the time delay is caused. It indicates that there is no problem even if there is.

The embodiments described so far are based on the assumption that the lens is not driven at all during the accumulation time and the calculation time. In that sense, it can be said that the tracking drive method is based on the intermittent drive. In the case of intermittent driving, since the processing is time-sequential, the CPU does not need to perform multitasking, and in that sense, it can be said that it is extremely superior. Further, when the power source for driving the lens is shared with the power source for operating the normal camera, for example, there is a constraint that the motor for driving the lens must be stopped during film winding. In this case, since the lens drive is inevitably inevitable, the intermittent drive tracking method described above is very suitable for a system having such a restriction. [Seventh Embodiment] However, in a system in which the lens can be driven at all times, it is also possible to track the movement of the object substantially continuously, and this makes the movement of the viewfinder look more like a name. There is a perceived advantage. In the following seventh embodiment, such a continuous tracking method will be described.

The main points of this embodiment will be briefly described. Basically, it is premised on the same drive mode as the normal intermittent drive.
When the defocus amount D _n is calculated, the defocus amount D _n is driven by that amount (which will be referred to as convergent driving) and the accumulation is started at the end of the driving. And when it is determined that there is object movement,
The correction drive amount associated with the movement of the object is uniformly driven at a constant speed during the entire period of accumulation, calculation, and drive. Therefore, the movement of the object is tracked by Nameraka. The point of continuous tracking is the same as in JP-A-60-214325, but the above-mentioned problems contained in this prior application have been solved. That is, in this case, since the lens movement is performed during the accumulation period, the correction for that amount is also necessary, but since the movement during the accumulation is constant speed, the correction is easy. Further, the drive only for tracking (hereinafter referred to as tracking drive) is not so fast, so that the influence of the time measurement error on the result is small.

21 and 22 are time charts when tracking is performed based on such a purpose. Figure 2
1 shows the case where the mirror-up operation is not performed, and FIG. 22 shows the case where continuous shooting is performed when the focus is achieved. That is, the difference between the two is whether the accumulation is started immediately after the end of the convergent driving or the accumulation is started after the period when the mirror is raised. In this embodiment, since the tracking drive is continued under any operation state, even if the state where the mirror is raised in the middle, the object movement amount during this period is corrected every moment, so far. There is an advantage that the correction for adjusting the exposure timing as described in the above embodiment is unnecessary.

Next, the parameters described therein will be described with reference to FIGS. 22 and 23 showing the same contents. The defocus D _n is found at the timing of the end of calculation, but its value corresponds to the distance between P and Q ′ at the midpoint of the accumulation time. Also, the n-th accumulation time is Tint (n), the time from the last accumulation end to the current accumulation start is T '(n-1),
Let T (n-1) be the time from the midpoint of the previous accumulation time to the midpoint of this accumulation time. I.e.

[0081]

[Equation 1]

Then, the amounts driven during these respective times are converted into image plane movements by Xint (n) and X '(n-, respectively).
1) and X (n-1). Therefore,

[0083]

[Equation 2]

It is Next, the flow of operation will be described with reference to the flowchart of FIG. Steps (1) (2) (3)
(4) and (5) are the same as before. Next step (6
In 0), the addition of the pulse corresponding to ΔP _n to Regis, which has been continuously performed at intervals ΔT sufficiently shorter than the accumulation time, is interrupted, that is, when the tracking drive is performed during the accumulation / calculation. To stop this. In step (61), T (n-1) and X (n-1) are calculated by the above equation.
To calculate. In order to be able to do this, it is necessary to read the value of the timer and the value of the event counter in advance at the timing of the start and end of the accumulation, so that the values Tint (n) and T '(n-1) described above can be read. , Xint (n),
X '(n-1) can be calculated, and therefore T (n-1), X (n
-1) can be calculated. Then, in step (62), FIG.
The convergence insufficient amount calculating means 100a, convergent shortage P _n is calculated by the following equation _{P n = D n + X (} n-1) -D n-1. The step (63) corresponds to the object movement judging means 100b, and judges the presence or absence of the object movement by the method as described in the first and second embodiments. If there is an object movement, the flag corresponding to the movement is set to IDO = 1 in step (64), and the object movement amount ΔP _n per unit time ΔT is calculated by the following equation in step (65). ΔP _n = P _n * ΔT /
T (n-1) In this embodiment, this step (6
5) corresponds to the object movement correction amount calculation means 100c. In step (66), the content of the event counter is set to zero (Event = 0), and the number of pulses corresponding to 〓D _n 〓 is set in the register. At this moment, the lens drive is automatically started, but the moving direction of the lens is controlled by separately setting a flag according to the positive or negative of D _n .

Then, in step (67), the EVC interrupt which conditions the end of the convergence drive is permitted. Step (6
In 8), the operation of adding the number of pulses corresponding to ΔP _n to every Regis is performed at every ΔT, and this operation is continued until step (60) in the next cycle is reached. That is, the target drive amount constantly increases (decreases) at a constant speed from step (60) to step (60) of the next cycle. As a result, the lens is driven at a constant speed not only during the convergence drive, that is, during the accumulation / calculation, but also during the mirror-up period. Convergence drive is started from step (66), and the content E of the event counter which accumulates the feedback pulses from the monitor means
vent becomes equal to the register value Regis and an EVC interrupt occurs. In response to this, the process proceeds to step (70), and the subsequent EVC interrupt is disabled. Since the register value Regis continues to increase at a constant speed even after this, the lens continues the constant-speed tracking drive and the event counter value Event increases accordingly, that is, Regis
The value increases while maintaining the equilibrium state of Event. This state corresponds to constant speed tracking drive. Then the object moving in step (71) is a chromatic (IDO = 1), performs the focusing process ¬ in step (72) when it is determined that the defocus amount 〓D _n ¬ <[delta] _q in step (73) . The contents are permission of mirror up and lighting of the focus display for a certain period.

Next, at step (74), the data required for the time calculation is stored, and n = n + 1. Step (7
In 5), it is determined whether or not the mirror is currently in the mirror down state. If it is in the mirror down state, the process proceeds to step (2) to start the next accumulation. If it is determined in step (63) that there is no object movement, the process proceeds to step (76), but the description is omitted because it is the same as that in FIG. 20 thereafter.

As described above, in the present embodiment, when the object movement is detected, the lens is driven at a constant speed according to the object movement speed to cancel the component due to the object movement, so that the defocus amount calculated is calculated. It suffices to perform high-speed non-constant speed drive (convergence drive) after the end of the calculation. Then, when the convergent driving is completed, the next constant speed driving is started, and at the same time, the accumulation is restarted. Since it is such a drive type, it not only gives a good impression of following the name change to the movement of the object, but also
There is no problem even if the timing of accumulation changes due to mirror up etc., and it is possible to take pictures that are always in focus. [Eighth Embodiment] Next, a method for discriminating the presence / absence of movement of an object will be described again in the following eighth embodiment. Regarding the contents of the object movement determination means 100b, the simplest form thereof has been described in the first embodiment, and the method with higher accuracy has been described in the second embodiment. Here, a method of more accurately determining the presence / absence of object movement by adding a temporal element will be described. Step (1005) in FIG. 5,
(1006) corresponds to this. That is, step (100
Step (1005) is the one in which 2) is set to the exact speed of object movement.

[0088]

[Equation 3]

The step (1003) is modified from the step (1003) to a strict speed comparison.

[0090]

[Equation 4]

It is Steps (1002), (100
5) mainly determines the presence / absence of movement of the object, and executes step (100
3) and (1006) mainly determine the presence / absence of a subject deviation. In actual use, step (1002),
Instead of (1003), each step (100
5) and (1006) may be used, or they may be used in series as shown in FIG. In that case, in steps (1002) and (1003), step (10
05) and (1006), the condition is loosely set, and 0 <k <k '<1 <r'<r.

Specific values of these coefficients are k≈〓
3 to 〓5, k '≒ 〓5 to 〓7, r' ≒ 〓4 to 2, r ≒ 2
It is good to set it to about 3. As described above, according to the eighth embodiment, the moving speed of the object is more rigorously determined and the comparison is performed, so that there is an advantage that the accuracy of determining whether or not the object has moved is improved.

[0093]

As described above, according to the present invention, even when the subject is moving in the optical axis direction of the taking lens of the camera, the amount relating to the subject image plane movement locus due to the movement of the subject is calculated, The lens is driven along this locus, and the drive is controlled to follow this expected locus both after the mirror is raised and focus detection becomes impossible, and during exposure. There are no restrictions on the time of day, no matter how long the release is performed, you can get in-focus pictures without any problems, and the release response is excellent.

[Brief description of drawings]

FIG. 1 is a block diagram of an automatic focus adjustment device that is a first embodiment of the present application.

FIG. 2 is a relationship diagram showing a state in which an automatic focus adjustment device tracks an object.

FIG. 3 is a detailed block diagram of correction means of the automatic focus adjustment device.

FIG. 4 is a flowchart of an automatic focus adjustment device.

FIG. 5 is a flow chart diagram of an automatic focus adjusting apparatus according to a second embodiment of the present application.

FIG. 6 is an explanatory diagram showing exposure timing in a known normal intermittent drive method.

FIG. 7 is a relationship diagram showing a state of a focusing operation of the automatic focusing control apparatus in the intermittent drive system.

FIG. 8 is a block diagram of a correction means of an automatic focus adjustment device according to a third embodiment of the present application.

FIG. 9 is a flowchart of the automatic focus adjustment device.

FIG. 10 shows a detailed explanatory diagram of S10 of FIG.

FIG. 11 shows a detailed explanatory diagram of S10 of FIG.

FIG. 12 is a relationship diagram showing timings during continuous shooting by the motor drive device of the automatic focus adjustment device according to the tracking drive system of the first embodiment.

FIG. 13 is a relationship diagram showing the timing at the time of continuous shooting of the automatic focus adjustment device which is the fourth embodiment of the present application.

FIG. 14 is a block diagram of correction means of the automatic focus adjustment device.

FIG. 15 is a flowchart of an automatic focus adjustment device.

FIG. 16 is a detailed view of a flowchart of the automatic focusing apparatus.

FIG. 17 is a relationship diagram showing a timing at the time of shooting by the automatic focus adjustment apparatus which is the fifth embodiment of the present application.

FIG. 18 is a relationship diagram showing the timing at the time of shooting of the automatic focus adjustment device which is the sixth embodiment of the present application.

FIG. 19 is a block diagram of correction means of the automatic focus adjustment device.

FIG. 20 shows a flowchart of the automatic focus adjustment device.

FIG. 21 is a relationship diagram showing a timing at the time of shooting by the automatic focusing apparatus when there is no mirror up.

FIG. 22 is a relationship diagram showing a timing at the time of shooting by the automatic focus adjustment device when there is a mirror up.

FIG. 23 is a relational diagram showing the timing at the time of shooting by the automatic focusing apparatus.

FIG. 24 is a block diagram of correction means of the automatic focus adjustment device.

FIG. 25 is a flowchart of the automatic focus adjustment device.

FIG. 26 is a block diagram of a conventional automatic focus adjustment device.

FIG. 27 is a relationship diagram showing a timing at the time of shooting by the automatic focusing apparatus.

[Explanation of symbols]

 100 ... Correction means 101 ... Focus detection means 102 ... Control means 103 ... Monitor means 104 ... Lens drive means 105 ... Lens information generation means

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G03B 3/00 A

Claims (2)

[Claims] 1. An image forming optical system for forming an optical image of a target object, and an image forming optical system including an image forming surface on which the optical image is formed and a predetermined image forming surface (film conjugate surface). A focus detection unit that outputs a defocus amount related to the distance in the optical axis direction, a lens drive unit that moves a focus matching optical system of the imaging optical system, a release member that instructs a mirror up and an exposure start, and the focus. Correcting means for receiving the output of the detecting means and correcting the influence of the movement of the image forming surface due to the movement of the target object in the optical axis direction; and the predetermined image forming surface for receiving the output of the correcting means. While following the movement of the image forming surface, and even when the exposure operation is started by the release instruction from the release member, the lens drive means is continuously driven without stopping before the exposure. As said Ren Automatic focusing device for a camera, characterized in that a control means for controlling the driving means. 2. The control means receives the correction amount of the correction means and controls the lens driving means so that the predetermined image plane moves along a movement locus of the image plane of the target object. Even if a release instruction is issued from the release member and an exposure operation is started, the control means drives the lens so that the predetermined image forming surface moves along the movement locus of the target object image forming surface even during exposure. An automatic focusing device for a camera according to claim 1, characterized in that it controls the means.