KR0144624B1 - Autoamtic focusing device - Google Patents

Abstract

In an autofocusing device, a focusing lens is driven to track a moving object to realize a focusing state based on focusing prediction made due to repetitive distance measurement.

The focus display is only performed when the focus lens is in focus and the object moves at a slower speed than the predetermined speed.

Description

Auto Focusing Device

1 is a block diagram showing the main parts of the autofocusing apparatus used in the camera and embodying the present invention;

2 is a graph illustrating the basic principles of a focused prediction system.

3 is a flow chart showing the process of the AF system in the focus prediction system,

4 is a graph illustrating the principle of preemptive tracking and catch-up tracking modes of a focused prediction system;

5 is a graph illustrating the calculation under preemptive tracking mode;

6 is a graph illustrating the principle of focus prediction for moving objects according to the integration time considered;

7 is a main flowchart of the focus prediction calculation,

8 is a flow chart of a focus prediction calculation that is executed specially after compensation is turned on when a moving object approaches the camera.

9 is a flow chart of the calculation after compensation is turned on when the second moving object approaches the camera.

10 to 17 are explanatory graphs of focus prediction calculations based on the moving state of a moving object and the result of lens driving;

18 is a graph illustrating an algorithm for a moving object moving away from the camera.

19 is a flowchart illustrating the calculation when a moving object moves away from the camera after compensation ON;

20 is an explanatory diagram for explaining the calculation when the second moving object is moved away from the camera soon after the compensation ON;

21 is a flowchart showing processing when the integration time is limited;

FIG. 22 is a flow chart showing the processing when a terminal point is detected during lens driving under focus prediction.

23 is a flowchart showing a defocus recalculation subroutine for checking whether a lens driving position is a focus position based on a focus prediction calculation,

24 is a flow chart for focus indication under focus prediction,

25 is a flow chart for the processing when the distance measurement is performed immediately after the descent under the shooting-continue mode and after another lens driving is performed after the release processing.

26 to 28 show graphs corresponding to the processing according to FIG. 25;

29 is a flow chart showing the processing for overlap,

30-32 are graphs illustrating a conventional system,

[Background of invention]

The present invention relates to an automatic focusing device for use in, for example, a photographic camera.

In recent years, there has been an enormous increase in cameras with AF (automatic-focus), and for single lens reflex cameras with interchangeable lenses, AF is indispensable, but generally for single lens reflex cameras. In this case, a so-called phase difference detecting method is adopted for autofocusing.

The AF function in which the upper bound has a detection method is executed in the following steps.

First, a pair of object images with spatial parallax are projected onto two photosensitive units, such as charge coupled devices (CCD), respectively, and the amount of light received by each photosensitive unit accumulates over time. Then, according to the difference between the two objects on each photosensitive unit, the distance difference between the sensing element (film corresponding surface 0 and the image plane (focusing position) of the photographing lens and its direction (defocusing / defocusing direction) on the subject) From the calculated amount and direction of defocus, the amount of driving of the motor required to cause the photographing lens to contact the image plane is obtained, on which the focus lens moves along the optical axis. do.

The number of pulses applied to the motor in this operation is obtained by the following equation.

P = Kv × D

Where P is the number of pulses applied to the motor

D is the amount of defocus

Kv is a so-called lens-shift amount conversion coefficient that indicates the relationship between the number of pulses for driving the motor and the amount of defocus, which is necessary to zero the defocus amount, and is a value inherent in each lens.

A conventional AF system will be described as represented above with reference to FIGS. 30 to 32. In each figure, the object position indicates the image surface of the photographing lens with respect to the subject at the position of the focus lens adopted as reference, and the focus position is the film corresponding surface at the position of the focus lens also adopted as reference.

Assume that the distance difference between the focal position and the object position, i.e., the focal point is detected as Do, as a result of the distance measurement performed at time 0 in FIG. 30, then, the defocus amount Do is zero. The lens is driven to do so. When the subject is static or stationary, the focal position will coincide with the object position as a result of lens driving.

Under this condition, interruption of release ON is carried out and the exposure begins after the time required to release the release-time support (t2), that is, the mechanical action to stop and lower the aperture and aperture in advance. . During exposure, the focal position and the on-object position are placed in coincidence, as can be seen in FIG.

However, when an object moves (especially when it moves in the lens driving direction), even if the integration and computation are performed once, the object continues to move while the lens is driven by such integration and calculation. Calculations and Results Lens driving must be carried out continuously to keep the focal point position on the object.

FIG. 31 shows a case in which the subject is moving at a constant speed from far to near. The closer the object is to the shooting lens, the greater the movement of the position on the object.

Assume that the distance difference between the object position and the focus position, that is, the amount of defocus is D1 at the point ①.

When the lens is driven by the degree corresponding to D1 after the time t ₁ elapses, the defocus amount D2 is obtained at the point ②. Likewise, after the time T ₂ has elapsed, the lens is driven by the amount corresponding to D2, and the defocus amount D3 is obtained at the point 3. In this case, the focal point at point ② corresponds to the position on the object at point ①, and since the object continues to move during the time (T ₁ ), the amount of defocus is D1 <D2 <D3. Thus, while the object continues to move toward the photographing lens at a constant speed, the defocus increases gradually every time the distance measurement is performed, and therefore the lens drive cannot sufficiently follow the movement of the position on the object.

In order to overcome this problem, the delay must be forgotten by predicting the amount of movement of the object position from the start of the integration to the completion of the lens driving as the lens is further driven. The LED etc ... then indicates that the object is within focus tolerance, allowing the operator to recognize that a focused picture can then be obtained.

However, even when the moving speed of the object is remarkably high, for example, when the moving speed of the object is higher than the driving speed of the lens, even if the focusing point is once implemented, the focusing display is formed as described above. Is located within the focusing tolerance only momentarily, and quickly leaves the focusing tolerance, making tracking impossible.

Thus, if a focal mark is always produced whenever the detected amount of defocus is within a certain focal tolerance, it is considered that the operator may be misleading because of the focal mark even though a well-focused picture cannot be obtained. Can be.

[Summary of invention]

Accordingly, it is an object of the present invention to provide an improved auto focusing device capable of properly driving a lens according to the movement of a subject, and also capable of displaying a focal point when a focusing state is implemented according to the onset of exposure.

According to the invention there is provided a focal lens which is moved along the optical axis of the device for this purpose; Driving means for driving the focus lens; Distance measuring means for obtaining an amount of focus deviation of the focus lens with respect to a subject;

Calculating means for calculating a relative moving speed of the object with respect to the focus lens along the optical axis based on the amount of defocus obtained by the distance measuring means; Drive control means for controlling the drive means to drive the focus lens to a position where a focal state can be realized for the object after elapse of lyric time based on the result calculated by the calculation means; Discriminating means for discriminating whether or not the speed of the object obtained by said calculating means is slower or faster than a predetermined speed; Display means for forming a predetermined display; And display control means for forming the predetermined display in a state where the speed on the object is slower than the predetermined speed.

EXAMPLE

Preferred embodiments of the present invention are described below with reference to the drawings.

1 is a block diagram showing the main part of a single lens reflex camera incorporating an autofocusing apparatus for carrying out the present invention.

When the AF switch S1 is closed in the illustrated camera, the potential of the port P71 of the CPU (central processing unit) changes to LOW and the operation of the AF system is started by drawing.

First, the distance measuring sensor 1 (which constitutes a CCD (charge coupled element) or the like) performs distance measurement. The obtained distance measurement data is transmitted to the port 1 of the CPU 3 via the interface 2, so that the amount of defocus and the direction are calculated by the CPU 3.

Then, the lens driving degree required for bringing the lens 100 into the focusing state is calculated from the K-value stored in the lens ROM 9 and the calculated focusing deviation.

In the case where the defocus is not obtained, it is checked whether the distance measurement data is valid, and if it is found that the data is invalid, an NG process such as indicating that the distance measurement has not been properly performed is performed. The distance measurement is then repeated.

Thereafter, it is determined whether the amount of defocus obtained is within the predicted focus tolerance, and if so, the LED driving circuit 10 is controlled through the port 74 of the CPU 3 to operate the positive-focus LED, and the release-ON Interruptions for processing are allowed.

When the amount of defocus obtained is out of the predicted focus tolerance, the interruption for release-ON processing is prohibited, the lens driving degree is set in the counter 6 and the lens driving circuit 4 is controlled to start the lens driving. . The rotational speed of the AF motor driven by the lens drive circuit 4 is monitored by the encoder 6 and is reduced until the value of the counter 6 becomes zero.

The AF motor stops here and the lens drive stops.

In the release-on interruption process, a series of control processes such as mirror up, exposure and mirror down are processed by the release control circuit 8 through the port 5 of the CPU 3 when the release switch SWR is closed. .

The shutter opens not the moment the release switch SWR closes.

There is a time delay between the closing of the release switch (SWR) and the beginning of exposure as the shutter opens, which is called a release-time-lag.

That is, it takes time to stop the aperture based on the aperture value set beforehand or manually by the exposure control calculation before opening the shutter.

When the subject is static or stationary, the position of the object corresponding to the photographing lens remains unchanged during the release-time-delay. Therefore, once the photographing lens is driven to the positive-focus position with respect to the object, no further defocus occurs, and therefore exposure can be performed under the positive-focus condition regardless of the length of the release-time-delay.

However, if the subject is moving on the optical axis of the photographing lens (hereinafter referred to as the moving object), when the position of the object corresponding to the photographing lens changes during the release-time-delay, ie when the release switch SWR is closed, Even if the photographing lens is placed under a constant focusing position, the object may move to an out of focus position when the exposure begins.

In this embodiment, in order to make the position on the object coincide with the focus position when the exposure is made (ie, after the release-time-delay has elapsed), the focus prediction is performed and this will be described in detail below.

In Fig. 2, the real curve shows the motion of the position on the object.

If the lens drive is controlled so that the focal position approaches a solid line after the release-time-delay has elapsed, exposure can be done under a normal-focused state.

Figure 2 shows the change in the object shifted to the left parallel to the degree corresponding to the release-time-delay by the point curve. If the lens is driven so that the focal position follows the point curve, the exposure always starts under the focal position, i.e., the focal position, corresponding to the object position each time the release switch SWR is closed.

3 is a flowchart showing the main processing of the AF system mounted in this embodiment.

When the processing sequence in this flowchart changes with the time of AF ranging, the flag AIS showing the time of AF ranging is removed at step S1.

In step S2, the distance measuring sensor 1 obtains the distance measuring data and the amount of defocus is thus calculated. Then, as mentioned above, in step S3, the lens driving amount (i.e., the number of AF pulses) is calculated and set in the counter 6.

In step S4, focus prediction calculation, which will be described in detail later, is performed.

In step S5, it is then checked whether or not the distance measurement data is valid.

If it is not valid, an NG process indicating that the distance measurement has not been properly performed is performed in step S5-1, and the process returns to step S2, where the distance measurement is repeated again.

In step S8, it is determined whether the amount of defocus is within the predicted focus tolerance.

If so, focus processing, such as illuminating the focus LED, is performed in step S7, allowing for interruption of the release-ON process.

In step S9, it is determined whether the so-called AF-one-shuttle mode is selected.

If so, the AF processing is paused waiting for the release switch SWR to close once the focal state is obtained.

In step S10, it is determined whether the compensation is ON, that is, the focus prediction mode.

If not, the process returns to step S2 and repeats the steps described above.

Furthermore, in step S11, it is determined according to the flag FFN whether the subject is approaching the lens 100 or away from the lens 100. If the subject moves away from the lens 100 (FFN = 1 in this case), the processing returns to step S2 as well.

When the object approaches the lens 100 in the focus prediction mode, it is determined whether the lens driving pulse number AFP of the current time is zero or not at step S12.

If so, if the number of lens drive pulses is not zero while the lens drive flag BFM is set to 1, the process returns to step S2.

This BFM flag determines whether the lens is driven or not.

If it is found in step S6 that the subject is not within the focusable area (i.e., the defocus amount is not within the predicted focus tolerance), the interruption for release-ON processing is prohibited in step S6-1. In step S6-2, it is determined whether the compensation is ON, that is, whether or not the focus prediction mode has been introduced. If it is found to be ON, it is determined at step S12 whether the lens driving pulse number AFP is zero or not. If AFP = 0, the process returns to the distance measuring process of step S2.

When the lens is to be driven because AFP is not zero, that is, when it is found that the focus prediction mode has not been introduced in step S6-2, the lens driving flag BFM is set to 1 in step S13. Processing proceeds. Then, a series of instructions starting from step S14 is performed for the lens driving process.

First, in the lens driving process in step S14, the lens driving amount is set in the counter 6 and the lens driving circuit 4 is controlled to start lens driving. The rotation speed of the AF motor operated by the lens drive circuit 4 is monitored by the encoder 5 and decreases its value in the counter 8. When the value becomes zero at the counter 8, the AF motor is stopped and lens driving is stopped.

After the lens driving is started, an interruption to the processing to be performed when the lens reaches the terminal point of the driving range is allowed in step S15. Such abort is described later in detail.

In step S18, it is determined whether PWM (pulse width modulation) control for the AF motor is necessary based on the number of pulses remaining in the counter 6. The PWM control is to control the AF motor so that the lens driving speed decreases in sequence until the lens driving is completed in order to accurately stop the lens at the position where the value of the counter 8 is zero, that is, the focal point position.

If the PWN control is not necessary, that is, if the lens is being driven, it is determined at step S17 whether compensation is ON or not. If the compensation is not ON, the overlap processing for repetitive distance measurement and calculation during the lens driving is driven in step S18 to update the value in the counter 6. The process then returns to step S16 to continue determining whether motor PWM control is necessary. The relationship between compensation ON and redundant processors will be explained later.

When it is determined in step S16 that PWM control is necessary, i.e., just before completion of the lens drive, PWM control is performed in the stem S16-1 and it is determined whether the lens drive is completed in the stem S16-1.

When the lens drive is completed, if the interruption of the processing to be performed when the lens reaches the terminal point is prohibited in step 16-3, the processing returns to step S2 for repetition of the distance measurement and subsequent instruction. Goes.

In the future, the focus prediction mode introduced when compensation is turned on will be described in detail.

In the focus prediction mode of this embodiment, the lens is driven according to two different algorithms, one of which is selectively adopted in some cases. One of them is catch-up tracking mode and the other is preemptive tracking mode.

When preemptive tracking mode is adopted, the release time-delay is not taken into account.

First, in referring to FIG. 4, the AF motor drive perth obtained at point ⓛ is denoted by A1. (The defocus amount on the film corresponding surface is multiplied by the K- value to drive the lens 100 to the focal position. Since the number of pulses applied to the AF motor is changed to the following, the number of pulses applied to the AF motor to remove the defocus amount is referred to simply as the pulse number or lens driving amount).

Assume that after the pulse A1 is applied to the AF motor for lens driving, and after the time T ₁ elapses, the pulse number A2 is obtained at the point ②.

The amount of movement of the object position from point ① to point ② corresponds to the number of pulses (A2).

Therefore, the object phase velocity (OBJsp) between points ① and ② is obtained as follows;

OBJsp = A2 / t1

Here, the position on the object is expressed as follows if the object velocity is constant at the point e after the time t ₂ from the point ②;

A2 + t2 × OBJsp

In the amount of movement of the position on the object determined by P2 for the time t2, if the situation becomes

P2 = t2 × OBJsp

The driving amount is expressed as follows;

A2 + P2

That is, the position at which the lens is driven by the AF motor by the driving amount of A2 + P2 is the object position after the time t ₂ .

On the other hand, P2 must be obtained before the lens driving amount is calculated.

Here, after the distance measurement data is obtained, the time required for the calculation of the lens driving amount is constant, and therefore, the total time including the lens driving time can be considered not significantly different in each case. Thus, on the assumption that the driving time of the calculation time and the current time, that is, the time t2, is equal to the driving time of the preceding time, that is, the time t1, the time t2 is substantially obtained by measuring the time t1. P2 is calculated.

The calculation described above relates to catch-up tracking.

However, as shown in FIG. 4, even at the point ②, the AF motor is driven by the amount of A2 + P2 so that the focus position and the object position coincide and the release switch SWR is closed at the point ③, even if the exposure is actual. It begins after the release of the release-time-delay.

Thus, another defocus occurs at the start of exposure and it is necessary to drive the lens with another preemptive force corresponding to the degree of movement of the object position during the release time delay.

This is preemptive tracking, which will be explained in detail later.

If the release time delay is RLt, then the expected number of pulses (T × P2) required to drive the lens further to the point where the object position coincides with the focal position when the release time delay has elapsed is Obtained together;

TXP2 + RLt × OBJsp

Here, as shown in FIG. 6, an integration is performed to measure the amount of defocus during the interval of time Tint, and various data are obtained from the result of the integration.

However, the point at which the focus deviation is obtained is considered at the point where the integration is started but shifted by Tint / 2 (that is, the midpoint of the integration time). So, if the lens drive amount is calculated in consideration of this, that is, if the release time delay used in the calculation is calculated as below,

RLt-Tint / 2

More accurate focus prediction is possible.

Therefore, the compensation in the calculation equation of TXP2 mentioned above should be as follows.

TXP2 + (RLt-Tint / 2) × OBJsp

Thereafter, the lens shift amount AFP2 is set to

AFP2 = A2 + P2 + Txp2

Lens drive will be performed under preemptive tracking mode.

Here, if the driving pulse number A3 actually obtained at point ③ coincides with the calculated Txp2, it means that the preemptive tracking is successful. (Actual velocity is not always constant, so A3 = Not Txp2).

Suppose that the driving pulse number A3 is obtained at the point ③ as a result of the integration and calculation in the next FIG. Then, as mentioned above, the time passing from point ③ to point ④ can be considered as the time (t2), and if the object velocity is constant, the position on the object is the same amount between point ③ and point ③ between points ③ and point ④ Move.

Therefore, the momentum of the position on the object between P3, that is, the point ③ and the point ④ is obtained as follows;

P3 = P2 + Txp3-A3

Therefore, the lens driving amount from AFP3, that is, from point ③ to point ④ is as follows;

AFP3 = P3 + Txp3-A3

The above can be applied to the motion of the position on the object between points n-1 and n and the following general equation is obtained;

Pn = Pn-1 + (Txp3-A3)

Txpn = (Pn)

AFPn = Txpn + Pn-An

Thus, Txpn can be found as a function of the on-plane momentum Pn, f (Pn).

Txp can be obtained in principle as follows;

Txp = (Pn / t) × RLt

However, as explained above, the release time delay used in the calculation should be calculated as follows to perform more accurate focus prediction.

RLt-Tint / 2

Thus, the general calculation of Txp mentioned above should be:

Txp = (Pn / t) × (RLt-Tint / 2)

Txp is obtained from the distance measurement data and is greatly influenced by the deviation of the distance measurement data. Therefore, in the present embodiment, the data obtained four times in the past immediately before performing the calculation are averaged according to the following equation.

Txp = (Txp + Txpn _-1 + Txpn _-2 + Txpn _-3 ) / 4

If there is a term for which historical data is not available, zero is substituted for the calculation to limit the Txpn value small.

7 is a flowchart of a subroutine for focus prediction performed in step S4 of FIG.

In step S201, the distance measurement data is checked. If the data is found to be invalid, the ranging time counter flag AIS is set again in step S226 and the processing returns to the main routine. For example, if this happens, the object will be considerably weaker, i.e. out of focus, so large distance data cannot be obtained.

Although the ranging data is valid, it is not necessary to enter the focus prediction mode if the AF one-sum mode is selected, i.e., if the focus processing is prohibited every time the correct focus state is obtained, the processing is performed in the main routine (step S201). Return to -1).

Moreover, even if the AF one-sum mode is not selected, the RM processing returns to the main routine through steps S224, S225 and S218 when the processing first comes to this routine (ie AIS = 0).

In step S224, the count flag AIS is set to 1 to indicate that the process has returned to this routine at least once. The timer 7 then operates to measure the time interval between subsequent distance measurements. The data used for the calculation is then removed in step S225.

When the number of distance measurements is one or more, the process proceeds from step S202 to step S203. In step S203, the time interval t is determined by the timer 7 from the previous distance measurement. Then, in step S204, it is determined whether the compensation ON, i.e., the focus prediction mode, has been introduced. When the compensation is not ON under the initial state, that is, when the focus prediction mode has not been introduced, the process proceeds to step S205. From step S205 to step S211, it is determined whether the subject can be treated as a moving object. In step S205, the defocus directions of the preceding time and the current time are compared. If it is found to be different, it is considered that the subject has changed the moving direction, and therefore the process returns to the main routine through steps S205 to S218 without determining whether the object can be treated as a moving object.

If the defocusing direction is the same, it is considered that the subject continues to move in the same direction, and the processing proceeds to step S208.

In step S208, it is determined whether the lens driving has been previously performed according to the flag BFM. When the lens driving is performed in the preceding distance measuring cycle, that is, BFM = 1, the processing proceeds to step S209, where the amount of moving on the object XX of the current cycle is set to An.

If the lens driving is not performed in the preceding cycle, that is, BFM = 0, the processing goes to step S207, where the preceding time defocus amount An-1 and the current time defocus amount An are compared. Determine if the position on the object is approaching the focal position.

If the position on the object is approaching the focal position (ie, An <An-1), the normal focus state will be obtained without introducing the focus prediction mode. The process then returns to the main routine via step S218.

If it is found in step S207 that the object position is moving away from the focus position or is found at the same distance (without changing the distance, if An <not An-1), the leading time defocus amount (An- 1) is removed from the current time defocus amount An at step S208, and the current momentum on the object is defined as XX = An-An-1.

Then, at step S210, the object phase velocity DBJsp, i.e., for one ranging cycle from time t.

XX / (K value × t)

Determine if is greater than the expected value. Here, for example, during the period of the sum of the intervals between successive distance measurements plus the release time delay (RLT), the predicted value corresponds to the speed at which the amount of movement of the position on the object corresponds to the predicted focal tolerance.

It is represented by the following equation.

Focal Tolerance / (t + RLt)

On the other hand, if the object velocity (OBJsp) is smaller than the predicted value, if the lens is driven based on the distance measurement of the current time, and the interruption to the release-ON process is performed, the object position is the release-time-delay Post exposure will remain within the focus tolerance at the onset of exposure.

Therefore focus prediction is not required.

On the other hand, the predicted value mentioned above may be set to a smaller value to make sure of the moving object. Moreover, although the judgment is generally approximate, the predicted value can be set corresponding to the speed at which the amount of movement of the object position during the release-time-delay coincides with the focal tolerance.

When the object velocity OBJsp is smaller than the expected value as described above, the process returns to the main routine via steps S225 and S218.

On the other hand, when the on-body velocity OBJsp is larger than the predicted value, it is then determined in step S211 whether the above-mentioned velocity determination is first performed.

If so, the process returns to the main routine via step S218.

If it is determined that the object phase velocity OBJsp is larger than the predicted value in the second or subsequent calculation cycle, the compensation is first set to ON, and the lens driving is introduced in accordance with the focus prediction mode.

In steps S212 and S213, the compensation ON and the flag C10 = 0 (this means the first cycle after the compensation ON DL has been performed, and the second cycle, if ON, C10 = 1) are set.

In step S214, the defocusing direction of the current time is determined, and the direction of movement of the object position is determined based on this.

On the other hand, in the case of post-focus (+), it is determined whether the subject is approaching the camera, and the preemptive tracking is started at step S222. On the other hand, in the case of pre-focus (-), the object moves away from the camera and the catch-up tracking starts at step S223.

In S215, a flag FFN indicating the relative positional relationship between the moving object and the camera is set to zero (0) to indicate that the object is moving toward the camera.

On the other hand, the flag FNN is set to 1 in S216 to indicate that the object is moving away from the camera. Subsequently, the process returns to the main routine via step S218.

When the routine returns to the current routine after compensation ON is performed, the processing branches from step S204 to step S219. When the object approaches the camera, the process of step S220 is executed, and the amount of focus deviation is calculated again in step S217 according to the routine of FIG. When the object moves away from the camera, the process of step S221 is performed and the process returns to the main routine through step S218.

In order to facilitate the next calculation in step S218, An and AFPn are respectively set and stored as AFPn-1 and the flag BFM is set back to zero (0).

8 is a subroutine performed in step S222 when the processing changes from the catch-up tracking mode to the preemptive tracking mode.

xx is set to Pn and is the amount of object motion (pulse number) used for calculation of this time (step S261). As expressed earlier, the driving amount corresponding to the release-time-delay Txpn is calculated as a function of the object momentum Pn (step S262), and then the lens driving amount AFP (i.e., the catch-up tracking mode at this time). The drive amount for changing to the preliminary tracking mode in is already calculated in step S263 as expressed in the description of the basic calculation.

In the focus prediction calculation, the compensation is performed on the basis of the value of FFN during the steps S215 and S216 of FIG. 7, and in the second and subsequent steps, the performed processes are distinguished according to the moving direction of the subject.

9 shows the processing of step S220, which is one of both, where the subject approaches the camera.

When the processing proceeds to this routine for the first time after compensation ON, the flag C10 is 0 (step S301), and in step S303, the processing enters the preemptive tracking mode in which the processing goes beyond the movement of the object position and has a focus position. Will decide. If the direction of defocus is different between the preemptive time and the current time, that is, this means that the process has entered the entire tracking mode, the flag C10 is set to 1 in step S304 and the process is step S305. Proceed to). If the out of focus direction is the same, the catch-up tracking mode continues and the process proceeds to step S323.

When the processing goes to the routine and the preemptive tracking mode is introduced, i.e., C10 is 1 (step S301) after compensation ON, at step S302, it is determined whether the defocusing direction is the same between the preemptive time and the current time. . If the defocus is different because the process has already entered the preemptive tracking mode in the preceding cycle, it means that the situation has changed from the tracking mode to the catch-up tracking mode, and the process proceeds to step S232. .

If the out of focus direction is found to be the same, it means that the preemptive tracking state remains, and the process proceeds to step S305.

In step S305, the amount of defocus An according to the distance measurement of this time is compared with the lens driving amount Txpn-1 corresponding to the release-time-delay equivalent of the running time.

This is a process for compensating for an error occurring when the calculation of Pn is performed at the object velocity, which is assumed to be constant above.

If An> Tspn _-1 , the actual physical momentum is less than Pn and the lens driving amount of the preceding time was determined to be too large, and the process went to the processing for the case where the preemptive tracking amount was too large (steps S314 and I and below). ).

If NO is determined in step S305, it means that the actual amount of motion on the object is less than or equal to Pn, or the processing is insufficient, or the processing for the case of lens driving amount of a suitable preemptive time is entered. In the next steps S306 and S314, the flag of BOV is a flag indicating what the determination result of the preceding step S305 is in the preceding cycle.

When BOV = 1, it indicates excessive movement, and when BOV = 0, it indicates insufficient or proper movement.

When the processing first came to this routine, the processing is performed at BOV = 0.

Step S307 shows the calculation when An> Txpn-1 is not valid for the current time and the preceding time shown in FIG. 5, and the same operation as described above with respect to FIG. 5 is executed.

As shown in FIG. 10, step S310 shows a calculation equation for the case where An> Txpn-1 at the preceding time but not at the current time.

In FIG. 10, the compensation amount (object movement amount) P2 is;

P2 = │A2- A1│,

Txp2 = f (P2),

AFP = Txp ₂ + (P2-A2)

Generalizing the above equation is as follows.

Pn = │An -An-1│

Txpn = f (Pn),

AFP = Txpn + Pn -An

When one of the above-mentioned steps S307 and S310 is performed, it is checked whether AFP <0 in the following steps S308 and S311. Then, when AFP <0, the process continues to step S312, where Pn = 0 and AFP = 0, respectively, and no lens driving is performed (no lens driving in the reverse direction).

In either case, at the next step S309 or S313, the BOV is set again based on the calculated value of the current time.

If the current time An> Txpn-1, the process moves to the loop of step S314 and subsequent. In this case, when An is larger than Txpn-1, the focal position advances by more than the release-time-delay corresponding, and it is unnecessary to drive the lens.

The compensation amount Pn and lens driving amount AFP modes are therefore set to zero in each case, and only the calculation of Txp is performed for the next time calculation.

In step SQ14, the determination is performed when the same as that performed in step S306.

Step S315 configures the calculations when An> Txpn-1 is formed at the current time as illustrated in FIGS. 11 and 12 rather than at the preceding time.

Where the compensation amount P2 is expressed as:

P2 = P1-(A2-Txp1)

Therefore, Txp ₂ = f (P2)

In general, the equation is;

Pn = Pn _-1- (An-Txpn _-1 )

Txpn = f (Pn)

After calculation of Txpn, Pn = 0 and AFP = 0.

Step S317 and below show the processing frame when An> Txpn ₁ is formed at the preceding time and the current time.

In step 317, the amount of An exceeding Txpn _-1 is within a predetermined focus tolerance used for determination of focus in step S6 of FIG. To determine if it is within, the number of pulses d, such as the sum of the focus tolerance and Txpn ₋₁ , is compared with An.

Step S318 is then performed when the amount of An exceeding Txpn _-1 is smaller, i.e., when the object position is within the focus tolerance after the release-time-delay elapses, and the case shown in FIG. Shows.

From that figure, P2 = A2-A1 and therefore,

Txp ₂ = f (P2)

Generalized, Pn = An-An _-1

Txpn = f (Pn)

After calculation of Txpn; Pn = 0, AFP = 0

If it is determined in step S317 that the amount of An exceeding Txpn _-1 is not within the focusing tolerance, then the processing goes to step S319.

In step S319, a determination as to whether or not the amount of An exceeding Txpn ₋₁ is out of focus tolerance occurs three or more times continuously. If so, the position on the object deviates greatly from the focus position or the direction or speed of movement on the object changes. It means that the position on the object within the focusing tolerance is lower, the compensation is OFF in step S322 in order to promote the focus prediction mode, and all the calculated data are erased. Then, as the data of the current time taken as the first data of AF, the focus prediction calculation is performed again.

Step S320 relates to the calculation in the case shown in FIG. 14 and the following is the same for step S318.

When it is determined in step S302 or S303 that it is not a pre-tracking state at the present time, it is determined in step S323 whether it was An> Txpn-1 at a preceding time from the flag BOV. When it is An> Txp-1 in the preceding time, the process goes to step S324.

That is the case where preemptive tracking is performed at the preceding time but the focal position is shown in FIG. 15 under the object position at the present time.

In this case, the compensation amount P2 is as follows;

P2 = A2 + A1

Therefore, TxP ₂ = f (P2)

Drive AFP is AFP = Txp ₂ + P2 + A2

If you generalize the above,

Pn = An + An-1

Txpn = f (Pn)

AFP = Txpn + Pn + An

If it is determined in step S323 that An> Txpn-1 is not the preceding time, the process goes to step S327. 16 is a case where a process for moving from the catch-up tracking state to the preemptive tracking state is attempted but fails. FIG. 17 shows a case where the wire tracking fails while the first tracking is in progress. In all cases the compensation amount P2 will be as follows;

P2 = Txp ₁ + P1 + A2

Therefore, Txp ₂ = f (P2)

The driving amount AFP becomes as follows;

AFP = Txp ₂ + P2 + A2

Generalizing the above;

Pn = Txpn _-1 + Pn-1 + An

Txpn = f (Pn)

AFP = Txpn + Pn + An

After the calculation of step S324 or step S327 is calculated, the flag C10 is set to zero in step S325, and the calculation of the current time in the next distance measurement will then be taken as the first compensation after compensation. The flag BOV is set in step S328.

In FIG. 7, both the step S221 and the step S233 are cases where the subject moves from near to far. If an object moves away from the camera at a constant speed,

The speed on the object decreases gradually, thus reducing the amount of lens driving.

In the above case, if the compensation is made in the release-time-delay equivalent preemption in a similar way as the object is approaching the camera, the probability of overcompensation is high. When overcompensation occurs, a post-focus result is shown, which is undesirable from the point of view of the photographing state. Thus, when the subject is moving away from the camera, focus prediction is basically performed without preemptive, that is, catch-up tracking, which is equivalent to release-time-delay.

18 is a graph showing the relationship between the on-object position and the lens driving pulse for an object moving away from the camera.

In Fig. 18, the number of motor driving pulses obtained at point ① is A1.

Subsequently, the pulse A1 is applied to the motor to drive the lens, and it can be assumed that the pulse number A2 can be obtained at point ② after the time t2 has elapsed.

The momentum of the position on the object between points ① and ② is A2 when converted to the number of pulses.

Therefore, the object velocity (OBJsp) between points ① and ②

OBJsp = A2 / t1

Here, when the object velocity is constant, it is assumed that the object phase position is a constant expressed as follows: the position on the object at the point ① taken as a reference and the point ③ at which time t2 elapses from the point ②.

A2 + t2 × OBJsp

As mentioned in the description of preemptive tracking, t2 is considered to be equal to t1 and the amount of motion on the object during t2 is considered to be equal to A2. Therefore, the driving amount is calculated as 2 x A2.

In other words, the focal position obtained by driving the AF motor by 2 x A2 from the point ② coincides with the position on the object after elapse of time t2. In this case, after the lens drive is completed and the exposure starts after the release-time-delay has elapsed, the focus position is not in the post-focus state when the exposure starts, ie, on the object even if the interruption treatment for the release-ON is performed. Located in front of the location. Thus no TXP calculations are performed and catch-up tracking is performed.

If it is assumed that lens driving of 2 × A2 is performed based on the defocus amount obtained at point ② as above, and the defocus amount A3 is obtained at point ③, the compensation for preemptive tracking is performed for the next driving amount. It doesn't work.

However, as in the preceding time drive, simply A3 × 2 is used.

It is a general equation for obtaining lens drive during catch-up tracking when an object moves away;

Lens drive amount (AFP) = 2 × An

(Here, it is assumed that t1 = t2, and the lens driving is performed at the preceding time)

19 and 20 show subroutines of steps S233 and S221 of FIG. 7, respectively.

In FIG. 19, the sum of the on-body momentum (pulse number) XX and the defocus amount An (pulse number) is used as the lens driving amount in step S271.

The object-like momentum XX is calculated at step S206 through step S209 based on whether the lens has been driven at a preceding time. XX = An if the lens was driven at a preceding time, otherwise XX = An-An-1. The lens driving amount calculated in step S271 in FIG. 19 never exceeds 2 x An.

In FIG. 20, the defocus direction of the current time is checked.

This is a check to avoid wave-compensation that is perceived when the defocusing direction is positive after completion of the lens drive, i.e., in the post-focusing state, despite the object moving away.

In the case of wave compensation, the compensation is turned OFF in step S277, the perforation data is cleared, and the new calculation will be performed with the data of the current time used as the first AF data.

After the over-compensation is checked, the amount of motion on the object is calculated according to whether the lens is driven within the preceding time as well as in steps S206 to S209 of FIG. 7 as well as in the following steps S273 to S275. (AFP) is set at step S276.

The above is the same as the case in FIG.

Here, determination of the peak point of step S6 of FIG. 3 is demonstrated.

The judgment depends on whether the defocus amount obtained at step S2 is within a predetermined focus tolerance, as described previously. In preemptive tracking mode, however, lens driving is always performed to have a preemptive equivalent of a release-time-delay, so even if the focusing state is obtained after the release-time delay has elapsed, there is not always a defocus amount in the focusing tolerance.

Also, although the amount of defocus is within the focal tolerance in the distance measurement, it does not mean that it is within the focal tolerance after the release-time-delay.

Therefore, the focus judgment cannot be obtained from the defocus amount.

Therefore, the defocus amount for the focal point determination is calculated in step S217 of FIG. 7, which will be explained in connection with FIG.

First, in step S51, the corresponding lens drive amount Txpn-1 equivalent to the release-time-delay obtained by the AF process at the preceding time is obtained by dividing the Txpn by K-values to defocus the image from the number of pulses. Changes to

Then, in step S52, regardless of the sign (+ or-) of the defocus amount (DEFOCUS) obtained by the distance measurement of the current time, the top defocus amount (DD) is added to this and the defocus amount is determined as the defocus amount. Is adopted. On the other hand, in the catch-up tracking, if the lens is not additionally driven by the amount corresponding to the release-time-delay, the calculation of the focus check defocus amount as described above is not performed.

According to the above, when the subject approaches the camera, the lens is driven as far as the release-time-delay corresponding, so that serious post-focus does not occur when the shutter release is turned ON, and shooting is always possible under the focusing state.

On the other hand, when the subject moves away from the camera, an algorithm for performing catch-up tracking is used, so that over-compensation resulting in post-focusing does not appear, and well-focused shooting is possible.

On the other hand, the interval for sampling the distance measurement data in the distance measurement operation can be shorter if the integration time is shorter, and tracking of the subject becomes easier.

So integration can be controlled as a time limit.

21 is a flowchart when the time limit is set to the integral.

That is, the maximum value Tint MAX of the normal integration time is set to the normal maximum integration time NORMAX (step S901). However, if the compensation ON is determined in step S902, the maximum integration time CONMAX for the compensation (this is less than the normal maximum integration time NORMAX) is used as the maximum value Tint MAX for the integration time (step S903). ). So at integral times shorter than normal, the distance measurement is performed during compensation ON. That is, the CCD integration with Tint MAX, which is regarded as the maximum integration time, is performed in step S904, and the obtained CCD data is an input for performing the calculation of the defocus amount in step S905.

Furthermore, as mentioned above, it can be imagined that the lens can be driven to the terminal point during tracking. Thus, during the lens driving, at step S15 of FIG. 3, the terminal point sensing circuit 11 (FIG. 1) is reset and the INT2 is allowed to stop.

If no pulse enters the terminal point sensing circuit 11 from the encoder 5 for a certain time, the INT2 interruption of INT2 in the CPU 3 occurs. That is, when the lens is driven by the terminal pointer during lens driving, no pulse is generated by the encoder 5 and therefore the terminal point sensing circuit 11 is turned ON and interruption of INT2 occurs.

22 is a flowchart of this interruption process.

If an interruption occurs, the lens driving is stopped, the terminal point detection interruption is prohibited, and the compensation is then turned off (steps S501 to S503). If no interruption occurs and the lens drive is completed in step S16-3 of FIG. 3, interruption of INT2 is prohibited.

FIG. 24 is a subroutine showing an example of the focus processing of step S7 in FIG.

Here the focus LED is assigned by the LED device circuit 10 to inform the operator that the camera is in focus.

It is preferable that a focus LED is provided in the viewfinder of the camera.

Here, if C10 = 1, the focal point display is performed and the process returns.

When C10 = 1, preemptive tracking is performed. And

MAX AFP Speed / K Value For OBJsp (mm / s)

In the formula, MAX AFP rate; Drive speed (pulse / s)

OBJsp; On-plane velocity (mm / s)

When is, focus display is always performed.

Thus, even during preemptive tracking, the focal point picture is always compensated if the focal point mark is ON (MAXS = MAX AFP speed / K value in the flowchart, OBJ = OBJsp).

If the on-body velocity exceeds the tracking speed limit, i.e.

MAX AFP Speed / K Value <OBJsp (mm / S)

In this case, the release-time-delay equivalent preemptive lens driving is not possible and therefore a well-focused picture cannot be obtained if the shutter is released, so the focal point indication does not appear in this case.

Since the preemptive lens movement equivalent to the release-time-delay is performed in the preliminary tracking mode, the AF switch S1 is first closed to drive the lens to the focal position, and the release switch SWR is closed at the completion of lens driving. At this time, the on-object position and the focal position necessarily coincide at the point of exposure start.

However, if the release switch (SWR) closes at a different time than the above or if the release switch (SWR) closes simultaneously with the closing of the switch (SW1) and the shutter release ON interruption is allowed after a certain time has elapsed following the lens driving. The starting point of the release-time-delay previously estimated does not match the actual timing of the shutter release ON interrupt. Moreover, the release-time-delay is not taken into account in the catch-up tracking mode. Thus, in such a case, the on-object position and the focus position do not always coincide when the exposure is initiated. For this reason, more accurate focus can be achieved if the lens is designed to be driven for as much as possible even during the release time delay.

Moreover, when the picture is taken continuously in preemptive trikang mode, high tracking cannot be achieved if the AF operation resumes after the exposure mirror is lowered and the film is finished winding.

Since the distance measurement is possible again after lowering in advance, it must be started immediately after the mirror lowering, regardless of whether the film winding is not completed. Thereafter, it should be executed by the sum of the number of driving pulses obtained by the distance measurement of the present time and the preceding time before the shutter release, and thus the tracking degree is improved.

Fig. 25 is a flowchart of the release-ON interruption process prepared in consideration of the above.

26 and 27 show the state of the controlled lens driving in this flowchart.

FIG. 26 shows a case where a release-ON interruption occurs during lens stop, and FIG. 27 shows a case where a release-ON interruption occurs during lens driving.

In step S8 of FIG. 3, an interruption to the release-ON process is allowed, and the process starts by an interruption caused by the shutter release-ON signal from the release switch SWR.

First, mirror raising and lens iris control are executed in step S601, and it is determined in step S602 whether compensation is turned on. When the compensation is off, the normal shutter release stage and the film winding during mirror lowering are executed in steps S603 to S605 to complete the interruption processing.

When the compensation is ON, it is determined in step S607 whether the lens is driven.

Based on this determination, the lens driving amount AFP is set again in step S608 or S609.

If the lens is not driven, the amount of object movement as from the completion of the previous time lens driving in step S608 is based on the elapsed time (tt) from the previous time lens completion according to the following formula as shown in FIG. Is calculated.

OBJsp × K value × tt

The obtained value is newly set in AFP.

On the other hand, if the lens is driven, the equivalent is already driven in step S609,

(AFP-Dar)

Dar: Remaining lens drive amount

AFP: Current lens drive setting

Is the lens driving amount (the same applies to step S608 above)

OBJsp × K value × tt

Subtracted from and executed for a time tt as shown in the preceding time lens drive completion as shown in FIG. 27, and the result is set to the new lens drive amount AFP.

When the newly set AFP in step S608 or S609 exceeds the maximum number of pulses M × M that can be driven during the release-time-delay, in step S611, AFP = M × M is set.

In accordance with the AFP set as described above, the lens is driven and exposure is executed (steps S612 and S613).

When the mirror lowering is completed (step S614), the next distance measurement, i.e., integration data input and calculation, is performed in step S615 simultaneously with the film winding, and the number of defocus pulses An is step S616. Is calculated from

Here, referring to FIG. 28, the operation of increasing the tracking degree by means of starting the next tracking operation immediately when the distance measurement is possible after the shutter release is completed is described.

That is, if the film winding is completed following the completion of the shutter release under the tracking mode, the tracking degree cannot rise if the next time distance measurement calculation is started.

Since the distance measurement is possible after the advance in advance, the shutter release starts at t1 after the advance in advance at t0, and at t11 when the mirror lowering is completed, the distance measurement is started and the defocus pulse An is obtained. The defocus pulse number An-1 obtained by the previous distance measurement is added to the defocus pulse number An and the result is used as a new drive pulse number AFP.

In this way, t2- than when the tracking operation is described by the dashed line in FIG. 28 where the next distance measurement starts after t ₂ when the film winding is completed continuously in the mirror descent as described by the solid line in FIG. You can take it as fast as t11.

The AFP is then taken as the sum of the previous time defocus amount (An-1) and the current time defocus amount (An) (step S617), the flag AIS is cleared, the compensation is turned off and the release-on-stop The process is completed (step S618). After completion of the interruption, the process moves to the LMOV in FIG. 3, and the lens is driven by the drive amount AFP.

29 is a flowchart showing a series of instructions for the so-called overlapping process in which the next distance measurement is repeated, while the lens is driven to obtain a more accurate driving amount.

If the first distance measurement measures an object distant from the focal point at that time, the defocus amount obtained itself contains a wider error, so that the acquired lens drive amount is not accurate and therefore the focusing operation is performed satisfactorily. It can't be.

Thus, the overlap processing is executed by updating the lens drive amount even when the lens is driven to perform correct focusing operation.

Similarly, the number of the original output lens driving pulses continuously determined by the driving of the lens is set in the counter 6. While the lens is being driven, the CCD integration starts.

The number of lens drive pulses remaining on the counter 6 at the time when integration is started in step S701 is taken as C1, and the number of lens drive pulses remaining on the counter 6 at the completion of integration is set to C3.

The CCD integral data is input at step S702, and the amount of defocus is obtained by calculating the CCD integral data at step S703. In step S704, the number of AF pulses is calculated and obtained based on the defocus amount in the same manner as in step S3 of FIG. 3, and the calculated value is taken as Cx.

In the calculation of Cx, the number of lens driving pulses of the counter 6 is taken as C4.

In step S705, the number of lens driving pulses for updating the number of lens driving pulses of the counter 6 is obtained by the following equation.

C2 = (C1 + C3) / 2

A = Cx-(C2-C4)

A is the number of update lens drive pulses set in the counter 6 in step S706, and the processing is completed.

On the other hand, when the compensation is ON, ie, in the tracking mode, the overlapping process is not executed, as apparent in steps S17 and S18 in FIG. This is, as already mentioned, redundant processing required when the defocus amount is large, but when the compensation is ON, the focus tracks the position on the object, so the amount of defocus is not very extensive. Furthermore, the AFP value obtained for tracking is updated by the AFP calculation performed by the superposition processing executed in the routines other than the main routine, so that the tracking operation itself becomes impossible.

With the auto focusing device mounted on the camera as described above, the focusing lens is controlled in the same way as the position on the object moves at a speed that is ahead of a predetermined one, that is, when the subject is a moving object, and tracking with two different algorithms is performed. .

That is, when an object approaches the camera, tracking is selected first, but the focus lens is moved under the condition that it is equal to the release-time-delay. On the other hand, irradiation tracking, in which the lens driving is not performed first, is selected when the object moves away from the camera.

Thus, even if the subject is a moving object, a precisely focused picture can be taken.

When entering the tracking mode, it is carefully determined that the subject is a moving object by repeating the measurement of the velocity on the object more than the prescribed number.

Moreover, even if the focus lens is already positioned within the focus tolerance and the focus point is configured, the focus lens is driven to track the moving object to achieve a complete focus state even if the processing is in tracking mode.

The release-time-delay used to track the calculation is obtained by considering the integral time versus distance time, where more flexible tracking operation is possible.

If the release-on interruption does not occur immediately upon completion of lens driving, the focus lens is driven by as much as possible within the release-time-delay, where less defocus can be made.

Moreover, in the case of a continuous picture, continuous and suitable tracking can be executed by starting a distance measurement for the next picture at the time during which the shutter release operation for the current picture is executed, for example, at the completion of the mirror lowering.

During the tracking operation, the focus point indication is made when the focus point is obtained and tracking is possible. It is desirable to illuminate the LED for the focal point indication that can be recognized by the camera's finder.

In the above-described embodiment, when it is determined twice that the on-object velocity exceeds a predetermined value, the processing tracks with more than a focal point, and may be set beyond a number other than two. Furthermore, if the number of times of lens driving during the tracking operation exceeds the predetermined value is determined three times, when the tracking is completed, such as when the tracking is not properly performed, the predetermined number other than the number three may be set. There is a possibility that the integration / calculation time is too long so that continuously executed lens driving cannot follow the movement on the object.

Thus, integration time is limited during tracking to reduce total distance measurement time, where tracking is effectively executed.

Moreover, overlapping processing is required when the speed on the object is narrow and the lens driving amount is relatively large. However, if the amount of lens driving required during tracking is normally small and the amount of driving required is quite large, tracking may not be performed because the object phase velocity is too large. Therefore, the superposition processing cannot be executed under the tracking mode which ensures the tracking lens driving force.

On the other hand, in the above embodiment, the case where the shutter release is executed during the establishment of the focusing condition, that is, the focus-priority case is also described. Of course, the present invention applies to shutter-release priorities that can be implemented even when the shutter release ignores the focus state.

In the latter case, steps S6-1 and S8 in FIG. 3 should be omitted to enable release-ON interruption.

Claims (17)

A focus lens movable along the optical axis; Driving means for driving the focus lens; Distance measuring means for obtaining an amount of defocus of the focus lens with respect to a subject; Determining means for determining a relative moving speed on the subject along the optical axis based on the amount of focus derivation obtained by the distance measuring means; Driving control means for controlling the driving means in accordance with the movement of a moving subject to drive the focus lens based on the determination of the determining means to obtain a fixed focus state after a predetermined time elapses; Discriminating means for discriminating whether the determined on-body speed is less than a predetermined speed; And operating means for providing a user with a predetermined proof that the speed on the subject is greater than a predetermined speed. The autofocusing apparatus according to claim 1, wherein the subject image speed is evaluated based on the moving speed on the moving subject formed by the focus lens, and the predetermined speed is the maximum speed at which the focus lens can be driven. The operating means according to claim 1 or 2, wherein the operation means provides a visual indication to the user when the determined subject image speed is less than the predetermined speed and does not provide a visual indication when the determined subject image speed is larger than the predetermined speed. Auto focus window, characterized in that further configured as a display means in response to. 4. An autofocusing apparatus according to claim 3, wherein said display means is comprised of a liquid crystal display. 5. The apparatus of claim 4, further comprising other discriminating means for discriminating whether or not a focal state is obtained after a lapse of a predetermined time, wherein the visible display is less than the predetermined speed on the subject, so that the other discriminating means is provided. An autofocus device, characterized in that the focus display provided when determining the focus state. 3. An autofocusing apparatus according to claim 1 or 2, wherein said discriminating means performs said discriminating in consideration of a predetermined tolerance. The autofocus apparatus according to claim 1 or 2, wherein the predetermined evidence that the speed on the subject is greater than the predetermined speed can be provided only for the relative movement of the subject toward the lens. The method of claim 1 or 2, wherein the driving control means evaluates the driving amount of the focus lens according to an away algorithm for relative movement of a subject away from the lens in order to bring the focus lens into a focused state when the lens driving is completed. First means; And second means for evaluating the driving amount of the focus lens according to a two-way algorithm for the relative movement of the subject toward the lens in order to bring the focus lens to a fixed focus state at any time after the lens driving is completed. Auto focusing device. 9. The method of claim 8, wherein the away algorithm is comprised of a first algorithm, and the forward algorithm is comprised of a first algorithm and a second algorithm for merging a compensation factor related to a release time delay prior to the actual start of exposure. Auto focusing device characterized in. 9. The autofocus window of claim 8 wherein said first algorithm comprises a catch-up tracking calculation and said second algorithm comprises a preemptive tracking calculation. 9. The autofocus apparatus of claim 8, wherein the predetermined time is a release time delay between the release operation and the exposure start. 12. The method of claim 11, wherein the second means evaluates the driving amount to include an additional lens driving amount related to the release time delay, and the additional lens driving amount is obtained by taking an average of those continuously obtained in a predetermined number of hours. Autofocusing device, characterized in that. The autofocusing apparatus according to claim 1 or 2, wherein the focusing state is provided with a predetermined tolerance. 3. The apparatus according to claim 1 or 2, further comprising check means for checking whether a defocus amount obtained by said distance measuring means is effective; And the drive control means is disabled when the defocus amount checked by the check means is invalid. 3. An apparatus according to claim 1 or 2, further comprising an end discrimination versatility for determining whether the focus lens has reached the end of its driving range; And the drive control means are disabled when the end discrimination means determines that the focus lens has reached the end of its drive range. 3. The distance measuring method according to claim 1 or 2, wherein the distance measurement is performed according to a phase difference detection method, and the amount of light received from the subject is integrated to calculate a defocus amount, and the time required for the integration is determined by the driving control means. If enabled, auto focusing device characterized in that it is limited to a predetermined length. 3. An apparatus according to claim 1 or 2, further comprising: overlap control means for repeatedly executing the distance measurement and determination during lens driving to re-evaluate the drive amount to obtain a focal state; The overlap control means is disabled when the drive control means is enabled.