JPH04258909A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To quickly execute focusing by starting a range-finding action again toward a next releasing action at some point of time after releasing. CONSTITUTION:When release-ON is executed, when the focusing is attained, by an automatic focusing function, a shutter is not opened in the moment of light but it is actually opened after a release-ON signal is read. There is time difference until exposure is started. In the case that an object moves, anticipating release control processing is executed in order to align the image position of the object with a focusing position. That means, in the case of a following-up mode, following-up that a lens for focusing is moved to a position based on defocus quantity by a range-finding means 1 is executed when the moving direction of the object becomes distant from a camera. When the moving direction of the object is the direction toward the camera, the lens for focusing is moved o an anticipating point by as much as the previous time difference.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention provides an automatic focusing function (AF).
AF (AUTOMATIC function), for example, an AF (AUTOMATIC
This invention relates to a device for accurately moving a focusing lens of a camera to a focusing position.

0002

BACKGROUND OF THE INVENTION In recent years, the number of cameras equipped with an AF function has increased significantly, and the AF function is becoming essential even in single-lens reflex cameras with interchangeable lenses. Single-lens reflex cameras generally employ AF using a phase difference method. AF using the phase difference method is performed in the following procedure. First, a subject image is projected onto a detection element (such as a CCD) having two light receiving sections, and the amount of light is
integrated over time. Next, based on the phase difference between the two subject images on each light receiving section, the distance difference between the detection element (film equivalent surface) and the imaging plane formed by the photographing lens facing the subject and its direction (defocus amount and defocus direction) are calculated. The amount of motor drive required to drive the lens to the in-focus position is determined from the direction of the calculated defocus amount, and the lens is driven along its optical axis so that the image plane coincides with the film equivalent plane. be done. The number of pulses applied to the motor at this time is determined by the following equation. P=Kv×D

[0003] Here, P is the number of drive pulses applied to the motor, and D is the amount of defocus. Kv is called the lens movement amount conversion coefficient (K value), and is a coefficient for calculating the number of pulses to drive the motor by the amount necessary to move the lens to the in-focus position from the above defocus amount and direction. , is a value specific to the lens.

FIGS. 30 to 32 are diagrams illustrating a conventional AF system configured as described above, and the subject image position in each diagram refers to the position of the subject image with respect to the position of the focusing lens. This is the image formation position, and the focus position indicates the position of the film equivalent plane with respect to the position of the focusing lens. In FIG. 30, assume that as a result of distance measurement at time t0, the distance difference between the focus position and the subject image position, that is, the defocus amount, is D0. Then, the lens is driven to make this defocus amount D0 zero. Since the subject is stationary, the focus position and the subject image position match as a result of lens driving. In this state, if the release ON interrupt processing is performed at time t1, and exposure is actually started at time t2 after the release time lag, that is, the time required for mechanical drive to raise the mirror and stop the aperture, has elapsed, then the exposure is actually started at time t2. As shown, the focus position and the subject image position at the start of exposure t1 always match.

However, when the subject is a moving body (one that moves in the direction in which the lens is driven), integration and calculations are performed, and based on the results, even while the lens is being driven for focusing, the subject remains In order to continue moving, it is necessary to repeat the integration, calculation, and lens driving processes.

FIG. 31 shows a case where a subject is moving from a far place to a near place at a constant speed, and the amount of change in the subject image position increases as the subject approaches the photographic lens. In this case, it is assumed that the distance difference between the subject image position and the focus position at point 2, that is, the defocus amount, is D1. The lens is driven by the amount corresponding to this D1, and the time t
It is assumed that when the defocus amount is calculated at point ■ after one elapse, D2 is obtained. Similarly, the lens is driven by an amount corresponding to D2, and the defocus amount D3 is determined at the next point (■) after time t2 has elapsed. Here, the focus position when calculating the defocus amount at point ■corresponds to the subject image position at point ■, and since the subject is moving during time t1, When moving at a constant speed, the defocus amount is D1<D2<D3.
The distance increases gradually each time distance measurement is performed, resulting in a problem that the lens drive cannot sufficiently follow changes in the position of the subject image.

[0007] In order to solve this problem, it is necessary to predict the distance that the object will move during the time from the start of integration to the time when the lens drive is completed by performing calculations, and to drive the lens by taking this amount into account. Therefore, various methods have been considered to solve the problem of tracking delay as described above. In such a case,
It is considered that the ideal state of the above method is for the focus position after each lens drive process to match the position of the subject image.

However, if ideal tracking focusing is performed,
Even if exposure is started when the focus position and subject image position match, when continuous shooting is to be performed, it is necessary to perform distance measurement for the next shooting.

However, in the conventional method, there is a problem that the distance measurement operation for the subject is not performed during the time required for processing the release operation from the release ON to the end of the winding, and therefore the tracking operation is interrupted during that time. Ta. Generally, a moving subject does not stop its movement in response to a release operation, but usually moves continuously. Therefore, even if you perform a distance measurement operation and drive the lens again after the release operation has been completed, the subject image position will have deviated significantly from the focus position at that point, and it will take longer to track the subject again. This takes a long time, and the problem caused by the delay in resuming distance measurement is particularly serious when the moving speed of the subject image gradually increases and the subject approaches from a distance.

0010

[Object of the Invention] The present invention has been made to solve these problems, and it is possible to obtain a photograph with better focus even for a moving subject, and also to make it possible to obtain a photograph with better focus even for a moving subject. It is an object of the present invention to provide an automatic focus adjustment device that can quickly perform the focus adjustment by quickly restarting the distance measurement operation.

[0011]

SUMMARY OF THE INVENTION In order to solve this problem, the automatic focus adjustment device of the present invention includes a focusing lens movable in the optical axis direction, and a distance measuring device for determining the amount of defocus for a specific subject by the focusing lens. means, a calculating means for calculating a relative moving direction and moving speed of the specific subject in the optical axis direction based on a plurality of defocus amounts obtained by the distance measuring means, and a calculation result of the calculating means; a drive control means for driving the focusing lens to a position where the object is in focus after a predetermined period of time has elapsed from the current position; and a release means for performing exposure;
The distance measuring means is characterized in that when the release means starts the release operation, the distance measuring means starts the distance measuring operation after a specific time has elapsed and before the release operation ends.

Furthermore, when the release means includes a movable mirror, the specific time can be the time required for the mirror that has been raised to come down from the start of the release operation of the release means. Further, when the moving direction of the subject is in the direction away from the camera, tracking is performed by moving the focusing lens to a position based on the defocus amount by the distance measuring means, and when the moving direction of the subject is in the direction approaching the camera. In some cases, advance tracking may be performed in which the focusing lens is moved to a point ahead by a release time lag.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the main parts of an AF camera in which an automatic focus adjustment device of the present invention is implemented. AF
When the switch S1 is turned on and the potential of the port P71 of the CPU 3 becomes LOW, the operation of the AF system is started. Via the interface 2, the distance measurement sensor 1 consisting of a detection element such as a CCD measures the distance, and the obtained distance measurement data is input to the CPU 3 through the port 1. The CPU 3 performs calculations to determine the defocus. The amount is calculated. Next, the lens driving amount is calculated from the K value stored in the lens ROM 9 mounted in the lens 100 and the defocus amount calculated above. In addition, if the defocus amount cannot be determined, check whether the distance measurement data is invalid or not. If the data is invalid, perform NG processing such as displaying that the distance measurement was not performed correctly. configured to do so. At this time, distance measurement is performed again. Then,
It is determined whether the defocus amount is within a predetermined focusing width, and if it is determined that the defocus amount is within a predetermined focusing width, the CPU 3 port P
74, controls the LED drive circuit 10 and controls the focusing LED.
Focusing processing such as lighting up D is performed, and a release interrupt is permitted.

Note that if it is determined that the focus is not within the in-focus width, the release interrupt is prohibited and the lens drive amount is counted by the counter 6.
, and controls the lens drive circuit 4 to start driving the lens. The number of rotations of the AF motor rotated by the lens drive circuit 4 is monitored by an encoder 5, and when a counter 6 is decremented and the content of the counter 6 becomes 0, the rotation of the AF motor is stopped and lens drive is stopped.

[0015] When the release switch SWR is turned on, the interrupt processing for the release ON is executed by the port Por of the CPU3.
After t5, the release control circuit 8 performs a series of release control processes including mirror raising, exposure, and mirror lowering.

[0016] When the release is turned on when the automatic focus function focuses, in reality, the shutter is not opened at the moment the release ON signal is read, but the shutter is actually opened after the release ON signal is read. There is a time lag between the opening of the aperture and the start of exposure, which is the time required for the aperture to stop down to the aperture value set manually or by exposure control calculation, and for the drive to raise the mirror. "Release time lag"
It is called. ). When photographing a stationary subject, the subject's position will not change during this release time lag, so once focus is achieved, defocus will no longer occur regardless of the length of the release time lag. , the actual exposure is performed with the subject in focus. However, if the subject moves, it will move from the in-focus position during this release time lag, so defocus will occur when actual exposure is performed.

Therefore, in this embodiment, the release is ON.
After the interruption, the following method is used to match the subject image position and the focus position at the time when exposure actually starts (that is, after the release time lag has elapsed).

In FIG. 2, solid lines indicate movement of the subject image position. If you control the lens drive so that the focus position is located on the solid line after the release time lag has elapsed,
No matter when the release is turned on, exposure will be performed in the focused state. The curve indicated by the broken line in the figure is obtained by translating the solid line graph indicating the actual movement of the subject image to the left by the release time lag. If you drive the lens so that the focus position follows this broken line, no matter when the release is turned on, the release control process will always start at the focus position that is ahead by the release time lag, and the subject image will be at the focus position after the release time lag has elapsed. When the image reaches the point where it is in focus, exposure is performed.

FIG. 3 is a flowchart showing the main processing of the AF system of this embodiment. In this embodiment, the processing procedure is changed depending on the number of AF distance measurements, so first, step S (hereinafter referred to as "S") 1
At , the flag A1S indicating the number of AF distance measurements is cleared. In S2, distance measurement is performed via the interface 2 with the distance measurement sensor 1 comprising a detection element such as a CCD, and the amount of received light is integrated over time to obtain distance measurement data. The distance measurement data is input to the CPU 3 via port 1, and the CPU
3, a predetermined calculation is performed to calculate the amount of defocus. In S3, the lens driving amount (the number of AF pulses) is calculated from the K value stored in the lens ROM 9 mounted in the photographic lens 100 and the defocus amount calculated in S2 using the above formula. This lens drive amount is set in the counter 6. In S4, a moving object prediction calculation (described later) is performed.

Next, in S5, if the defocus amount cannot be determined, etc., a check is made to see if the distance measurement data is invalid. If the data is invalid, a message indicating that the distance measurement was not performed correctly is displayed. After performing NG processing such as
Returning to S2, distance measurement is performed again.

[0021] In S6, it is determined whether the defocus amount is within a predetermined focusing width, and if it is determined that it is within the focusing width, in S7, the LED drive circuit 10 is controlled via port P74 of the CPU 3. and performs focusing processing such as lighting up the focusing LED. In the next step S8, the release ON interrupt is permitted, and the release operation becomes possible.

S9 is a process for a so-called one-shot, and is a process for stopping the focusing process once the image is in focus.

Next, in S10, it is determined whether or not the correction is ON, that is, whether or not the follow-up mode is set. S if not in tracking mode
Returning to step 2, the CCD integration process is restarted.

In the case of tracking mode, it is determined in S11 whether the subject is moving in a direction approaching the lens 100 (camera) or not.
Alternatively, it is determined whether the camera is moving away from the lens 100 (camera) based on the contents of the flag FFN, and if it is moving away from the camera, the process returns to S2. Here, the case where the subject is moving away from the lens is shown as FFN=1. Follow mode in S10, S11
When it is determined that the subject is moving toward the camera, the current number of lens drive pulses (AF
P) is 0 or not. If the number of lens drive pulses is 0, the process returns to step 2, but if it is not 0, the lens drive flag BFM is set to 1. This is a flag indicating whether the lens has been driven.

If it is determined in S6 that the defocus amount is not within the predetermined focus width (that is, if the defocus amount is not within the predetermined focus width), after taking steps to prohibit the release operation in S6-1, It is determined in S6-2 whether the correction ON mode is in effect, that is, whether the tracking mode is in effect, and if it is ON, it is determined in S12 whether the lens drive pulse number AFP is 0 or not. AFP=
If it is 0, lens driving is not performed, and the process returns to distance measurement processing in S2.

If AFP is not 0 and the lens is being driven, or if it is determined in S6-2 that the tracking mode is not in effect, the lens drive flag BFM is set in S13 as described above.
Set it to 1. Then, lens drive processing from S14 onwards is performed.

In this lens driving process, first, S1
4, the lens drive amount is set in the counter 6, and the lens drive circuit 4 is controlled to start lens drive. In addition,
The rotation speed of the AF motor rotated by the lens drive circuit 4 is monitored by the encoder 5, and when the counter 6 is decremented and the content of the counter 6 becomes 0, A
The rotation of the F motor is stopped and lens driving is stopped.

After lens driving is started in S14 in this manner, in S15, interrupt processing is permitted when the focusing lens is driven to the end point of its driving range during lens driving. This interrupt processing will be described later.

[0029] In S16, the value of counter 6 is exactly 0.
The motor's PWM (Pulse Width Modular) controls the AF motor so that the lens drive speed is gradually slowed just before the lens drive ends, so that the lens stops accurately at the in-focus position.
tion) It is determined from the number of pulses remaining until focusing whether or not control is required, and when it is not required yet, that is,
When the lens is being driven, it is determined in S17 whether correction is ON. And when the correction is not ON,
In S18, overlap processing is performed, that is, distance measurement, calculation, etc. are further performed while the lens is being driven, and processing is performed to update the value of the counter 6, and judgment is made in S16, that is, judgment is made as to whether or not PWM control of the AF motor is required. repeat. However, S17
If the correction is ON in , the process returns to S16 without performing overlap processing. Note that the relationship between this correction ON and overlap processing will be described later.

[0030] If PWM control is required in S16,
That is, immediately before the end of lens driving, PWM control is performed in S16-1, and it is determined in S16-2 whether or not driving has ended.

When the lens driving is completed, interrupt processing at the time of end point detection is prohibited in S16-3, and the process returns to S2 to continue distance measurement processing.

The follow-up mode when the correction is ON in this embodiment will be explained below. First, an explanation will be given of the algorithm at the time when the camera enters the anticipatory tracking mode, which moves ahead by the release time lag from normal tracking focusing.

In FIG. 4, the number of motor drive pulses obtained at point (■) is assumed to be A1. The image plane defocus amount is K
By multiplying by the value, it can be converted to the number of pulses applied to the motor to drive the focusing lens to the in-focus position.In the following explanation, we will calculate the number of pulses applied to the motor to eliminate the amount of defocus. This will simply be called the "number of pulses" or the amount of lens drive. It is assumed that after this, a pulse A1 is applied to the motor to drive the lens, and after a time t1 has elapsed, the number of pulses A2 at point ■ is determined. ■
The amount of movement of the subject image from the point to the point ■ becomes A2 when converted into the number of pulses. Therefore, the object image movement speed OBJsp between the points ■ and ■ points is OBJsp=A2/t1. Here, the subject image position at point ■ after time t2 has elapsed from point ■ based on the subject image position at point ■ is expressed as A2+t2×OBJsp, assuming that the subject image speed is constant. Let P2 be the amount of movement of the subject during time t2, and P
2=t2×OBJsp, the driving amount is calculated as A2+P2. In other words, the point where the motor is driven by A2+P2 at point ■ coincides with the subject image position after time t2 has elapsed.

Note that this P2 must be calculated in advance at the time of calculating the lens drive amount. Here, the time required to calculate the lens drive amount after obtaining the distance measurement data is always constant, and it can be considered that the time including the drive time does not differ much each time. Therefore, assuming that the current calculation time and driving time, that is, time t2, are the same as the previous calculation time and driving time, that is, time t1, time t2 is obtained by actually measuring time t1, and P2 is calculated. do.

As shown below, even if the motor is driven by A2+P2 at point (■) to match the focus position and the subject image position, and the release is interrupted at that point, exposure will actually start only at the release. Since this is after the time lag has elapsed, it is necessary to move the focusing lens in order to further advance the focus position by the amount of movement of the subject image during that time.

When the release time lag is RLt, the number of advance pulses TXP2 required to advance the focus position by the amount of the release time lag from the subject image position is determined by TXP2=RLt×OBJsp, and if the motor is driven by that number of pulses, It's going to be a good thing. It should be noted that the release time lag RLt is from the end of lens driving to the start of exposure in each period from ■ to ■ in FIG. As shown in FIG. 6, in order to measure the amount of defocus, integration is performed during the time interval Tint, and each data is obtained based on the integrated value, but the actual amount of defocus is The obtained position is not the position at the start of the integration, but can be considered to be the measured distance value at a time point Pi that has elapsed by Tint/2 (ie, the midpoint of the integration time). Therefore, the above release time lag R
If Lt is configured to be corrected for this amount and calculated as RLt-Tint/2, more precise tracking will be possible. Therefore, the formula for calculating TXP2 above is TXP
A correction is added as follows: 2=(RLt-Tint/2)×OBJsp. From the above, the lens drive amount A at point ■
By setting FP2 to AFP2=A2+P2+Txp2, so-called trailing tracking, which simply adds correction for the amount of object image movement to the defocus amount, enters proactive tracking, which drives the lens in anticipation of the release time lag. If the number of drive pulses A3 actually determined at the point where time t2 has elapsed from point (2) matches the above-mentioned Txp2, it means that the number of drive pulses A3 is in advance by the release time lag. Note that in reality, since the moving speed of the subject image is not constant, A3=Txp2 is not always true.

Next, in FIG. 5, the result of integration and calculation ■
Assume that the number of pulses A3 is obtained at the point. Then, from the figure,
The difference between the subject image position corresponding to point ■ and the subject image position corresponding to point ■ (the amount of movement of the subject image) is calculated by considering that the time from point ■ to point ■ is the same as t2, as described above. Assuming that the movement of the image is linear, it is considered that the amount of movement from point ■ to the position of the subject image corresponding to point ■ is equal to the amount of movement of the image, so the distance of the object from the position corresponding to point ■ to the position corresponding to point ■ The movement amount P3 is calculated as P3=P2+Txp2-A3. Therefore, the lens driving amount AFP3 from the point ■ to the point ■ becomes AFP3=P3+Txp3-A3.

Based on the same idea, the following formula can be obtained as a general formula for determining the amount of movement of the object image and the amount of lens drive during proactive tracking. Pn=Pn-1+(Txpn-1-An)Txpn=f
(Pn) AFPn=Txpn+Pn-An Here, Txpn is a function f(Pn
) is required. In principle, Txp is Txp=(
Pn/t)×RLt. However, as mentioned above, as shown in FIG. 6, in order to measure the defocus amount, integration is performed during the time interval Tint, and each data is obtained based on the integrated value, so the actual defocus amount is The position from which the amount can be obtained is not the position at the start of the integration, but can be considered to be the measured distance value at the time point Pi after Tint/2 (that is, the midpoint of the integration time). Therefore, if the above-mentioned release time lag RLt is corrected by this amount and calculated as RLt-Tint/2, more precise tracking becomes possible. Therefore, the above Txp can be expressed as Txp=(Pn/t)×(RLt-Tint/2).

Furthermore, since Txp is determined from distance measurement data and is greatly affected by variations in the distance measurement data, in this embodiment, the immediately preceding four data are averaged and used according to the following equation. Txpn=(Txp+Txpn-1+Txpn-2+T
xpn-3)/4 Note that calculations are performed by substituting 0 for items for which there is no past data.

FIG. 7 is a flowchart of a subroutine for the moving object prediction calculation performed in S4 of FIG. The distance measurement data is checked in S201, and if the distance measurement data is not OK, the flag A1 for counting the number of distance measurements is set in S226.
Set S to 0, which indicates the first time, and return to the main processing. Examples of such cases include a subject with very low contrast, or a case where the amount of defocus is so large that distance measurement data cannot be obtained. In addition, when setting the AF one-shot mode as described above, that is, when performing control to stop the focusing process once the focus is achieved, even if the focus is once focused, the camera will follow the subject and perform the defocus process. There is no need to switch to continuous tracking mode, so S201-
If it is determined in step 1 that the mode is AF one-shot mode, the process directly returns to the main process. If it is not AF one-shot, and the process comes to this routine for the first time after entering AF mode, and it is determined in S201 that the distance measurement data is OK, it is determined that A1S=0 in S202,
The process moves to S218 via S224 and S225, and returns to the main process. At this time, in S224, the flag A1S for counting the number of distance measurements is set from 0 indicating the first distance measurement to 1 indicating the second and subsequent distance measurement, and from then on, A1S=
1 indicates that the processing is the second or more time, and
A timer 7 for measuring the distance measurement time interval is started, and each data for calculation is initialized in S225.

[0041] When the number of distance measurements reaches the second time or more, S202
The program then proceeds to S203, and in S203, the timer 7 measures the time interval t from the previous distance measurement. In S204, it is determined whether the correction is ON, that is, the tracking mode is in effect, but in the initial state, the correction is OFF, that is, the tracking mode is not in the mode, so the process advances to S205. S205 to S2
In routine 11, it is determined whether the subject image is to be treated as a moving object. In S205, the current and previous defocus directions are compared, and if they are different, it is considered that the subject image has changed its moving direction, and the calculation data is cleared in S225 without determining whether to treat it as a moving object. The process returns to the main process through S218. If the defocus directions are the same, it can be considered that they are moving in the same direction, and S
Proceed to 206. In S206, it is determined based on the flag BFM whether the lens was driven during the previous distance measurement. If the lens was driven in the previous distance measurement, that is, BFM = 1, the process advances to S209, and the current subject image movement amount XX = An, and if the lens was not driven last time, that is, BFM = 0.
In this case, the process advances to S207 and the previous defocus amount A is
By comparing n-1 with the current defocus amount An, it is determined whether the subject image is approaching the focus position. If the subject image is close to the focus position, it will be in focus sooner or later, even if it does not go into tracking mode, so S21
After step 8, the process returns to the main process.

On the other hand, in S207, if it is determined that the subject image is moving away from the focus position, or if it is determined that the subject image is equidistant, in S208, the current defocus amount An is changed from the previous defocus amount An. -1 is subtracted, and the current subject image movement amount XX=An-An-1,
In S210, from t obtained in S203,
Subject image speed O during one cycle from distance measurement to distance measurement
BJSP, that is, XX/(Kvalue×t) is determined and it is determined whether this is larger than a predetermined value. Here, the predetermined value is, for example, the amount that the subject image moves within the time period t from distance measurement to distance measurement plus the release time lag RLt, which is expressed by the formula, focusing width / (t + RLt). The speed matches the width. In other words, if the object image speed OBJSP is smaller than this value, if the lens is driven based on the current distance measurement and then the release ON interrupt processing is performed, the moving object image will start to be exposed after the release time lag has elapsed. Sometimes it is within the focusing range, so there is no particular need to track the moving object. however,
In order to reliably determine that the object is a moving object, the predetermined value may be set to a smaller value with a margin. Further, although the judgment is somewhat rough, the predetermined value may be set to a speed at which the amount by which the subject moves during the release time lag matches the focusing width.

As described above, when the object speed OBJSP is determined to be smaller than the predetermined value, the process moves to S225, and after clearing the calculation data, passes through S218 and returns to the main process. On the contrary, subject image speed OBJS
If P is larger than a predetermined value, it is determined in S211 whether or not this is the first time that the speed-related determination has been made, and if it is the first time, the process returns to the main process through S218. Then, when it is determined that the object image speed OBJSP is larger than a predetermined value in two or more distance measurement calculations, the correction is turned on for the first time, and the lens is driven according to the moving object tracking algorithm of the present invention. In S212 and S213, each correction is turned on and flag C1 is turned on.
0=0 (indicates that it is the first time the correction has been turned on.2
After the first time, C10 is set to 1. In S214, the current defocus direction is determined, and based on this, the moving direction of the subject image is determined. That is, if the defocus direction is rear focus (+), it is determined that the subject is moving closer to the camera, and advance tracking processing is entered in S222.

On the other hand, if the defocus direction is front focus (-), it is determined that the object is moving away from the camera, and a follow-up process is started in S223. Further, in S215, a flag FFN indicating the relative positional relationship between the subject and the camera is set to 0, indicating that the subject is moving closer to the camera. Also, in S216, the flag FFN is set to 1.
to indicate that the subject is moving away from the camera. Thereafter, the process returns to the main process via S218.

When the process reaches this routine after the correction is turned ON, the process moves from S204 to S219, and if the subject is moving closer to the camera according to the moving direction of the subject, the process proceeds to S220. Process and S2
In step 17, the defocus amount for focusing is recalculated using the routine of FIG. 23, and if the subject is moving away from the camera, the process of S221 is performed,
18 and returns to the main processing.

[0046] In S218, for the next calculation,
An is set to An-1, AFPn is set to AFPn-1, each data is stored, and the flag BFM is reset to 0.

FIG. 8 shows a subroutine in S222 of FIG. 7 when the mode shifts from the follow-up mode to the anticipatory mode. XX
is the object movement amount (number of pulses), and is set to Pn in order to use it in the current calculation (S261). As described above, the drive amount for the release time lag is calculated as a function of the subject movement amount Pn (S262), and in S263 the current lens drive amount (the drive amount for switching from trailing tracking to anticipatory tracking) AFP is calculated. The details are as already described in the explanation of the basic calculation.

In the second and subsequent moving object prediction calculations after the correction is turned ON, different processing is performed depending on the moving direction of the object based on the FFN value set in S215 and S216 in FIG. FIG. 9 shows the processing in S220 when the subject approaches the camera from a distance.

When this routine is passed for the first time after the correction is turned on, the flag C10 is determined to be 0 in S301, and it is determined in S303 whether or not proactive tracking has started beyond the movement of the subject.
will be judged. If the defocus directions this time and the previous time are different, it is determined that proactive tracking has started, the flag C10 is set to 1 in S304, and the process moves to S305. If the previous and current defocus directions are the same, it is determined that trailing tracking remains the same, and the process moves to S323. If this routine is entered for the second time or later after entering proactive tracking after correction is turned on, flag C10 is set to 0 in S301.
It is determined that this is not the case, and it is determined in S302 whether the defocus direction of the previous time and this time are the same. In this case, since the previous process has already been in the proactive tracking state, if the defocusing direction is different between the previous time and this time, the process has changed from proactive tracking to trailing tracking, and the process moves to S323. If the defocus direction is the same this time and the previous time, it means that advance tracking is continued as it is, and the process is performed in S3.
Move to 05.

In S305, the defocus amount An obtained by the current distance measurement is compared with the lens drive amount Txpn-1 corresponding to the previous release time lag. This is a measure to correct the error caused by calculating Pn on the assumption that the moving speed of the subject image is constant, as described above. If An>Txpn-1, this is a case where the actual movement amount of the subject image is smaller than Pn,
It is determined that the previous lens driving amount was too large, and the process moves to a case where the advance amount is too large (S314 and subsequent steps). Further, if the determination in S305 is NO, this means that the actual movement amount of the subject image is equal to or greater than Pn, and the process is performed when the previous lens drive amount was insufficient or appropriate. The flag BOV in the next S306 and S314 is a flag that indicates what the judgment result of the previous step (S305) was last time.If BOV=1, it is too proactive, and if BOV=0, it is insufficient or insufficiently proactive. This indicates that the amount was appropriate, and when this routine first comes, it is always processed as BOV=0.

[0051] S307 shows the calculation in the case where An>Txpn-1 is not satisfied both this time and the previous time, as shown in FIG. 5, and the calculation is performed as already explained with respect to the same figure. In S310, the previous An>Txpn− shown in FIG.
1, and this time it is not the case. In Figure 10, the amount of correction (amount of subject image movement)
P2 is P2=|A2-A1| and Txp2=f(
P2), the driving amount AFP is AFP=Txp2+(P2-
A2). The above can be summarized as follows. Pn=|An-An-1| Txpn=f(Pn) AFP=Txpn+Pn-An

[0052] In any case where the above steps S307 and S310 are performed, in the subsequent S308 or S311, AFP<
If AFP<0, the process moves to S312, where Pn=0 and AFP=0, and lens drive is not performed (lens drive in the opposite direction is not performed). In either case, in subsequent S309 or S313, the BOV is reset based on the current calculated value.

[0053] If An>Txpn-1 this time, the process moves to a loop starting from S314. In this case, An is T
Since it is larger than xpn-1, it is in a state that is ahead of the release time lag and does not drive the lens.
In any process, the correction amount Pn and drive amount AFP are both set to 0 and used for the next calculation, so Txp
Only the calculation is performed. In S314, the same case classification as in S306 is performed.

S315 is shown in FIGS. 11 and 12. Previously, An>Txpn-1 was not satisfied, but this time An>Txpn-1 was not satisfied.
In the calculation when xpn-1, the correction amount P2 is P2
=|P1-(A2-Txp1)| Therefore, Txp2=f(P2), and in summary, Pn=|Pn-1-(An-Txpn-1)|Txpn
=f(Pn) Pn=0 AFP=0.

[0055] For S317 and below, An>Txp both this time and last time.
The processing when the number is n-1 is shown. In S317,
Whether or not the amount by which An exceeds Txpn-1 is within the predetermined focusing width used to determine focus in S6 in FIG. To determine whether it is within the focal width, add the number of pulses for the focal width to Txp and A.
Compare n.

The next step S318 is when the amount by which An exceeds Txpn-1 is smaller, that is, when the position of the subject image after the release time lag has elapsed is within the focusing width, as shown in FIG. This is the calculation. From the same figure,
P2=|A2-A1|, therefore, Txp2=f(
P2). In summary, Pn=|An-An-1| Txpn=f(Pn) Pn=0 AFP=0.

If it is determined in S317 that the amount by which An exceeds Txpn-1 is not within the focusing width, the process moves to S319. In S319, if it is determined that the amount by which An exceeds Txpn-1 does not fall within the predetermined focusing width has continued three or more times, it is determined that the subject image position has deviated greatly from the focus position, or It is determined that the moving direction or moving speed has changed significantly, and the tracking mode is canceled as the possibility that the subject image will fall within the focusing width is low, so correction is turned OFF in S322 and all calculation data is cleared. . Then, the moving object prediction calculation is performed again using the current data as the data for the first AF. S320 is the calculation for the case shown in FIG. 14, and the content is S320.
It is similar to 318.

[0058] If it is determined in S302 or S303 that proactive tracking is not being performed this time, the flag BOV is checked in S323 to determine whether An>Txpn-1 last time.
It is judged by. Previous An>Txpn-1 in S323
If it is determined that it is, the process moves to S324. This is the case shown in FIG. 15, where the previous tracking was performed in advance and the current focus position is after the subject image. The correction amount P2 at this time is expressed as P2=A2+A1. Therefore, Txp2=f(P2), and the drive amount AFP becomes AFP=Txp2+P2+A2. To summarize the above, Pn=An+An-1 Txpn=f(Pn) AFP=Txpn+Pn+An.

If it is determined in S323 that the previous time An>Txpn-1 is not satisfied, the process moves to S327. FIG. 16 shows a case in which the transition from trailing tracking to anticipatory tracking was performed, but it was not possible to move ahead, and FIG. 17 shows a case where it became impossible to move ahead during anticipatory tracking. In either case, the correction amount P2 is P2=Txp1+P1
+A2. Therefore, Txp2=f(P2),
The driving amount AFP is AFP=Txp2+P2+A2 (S327). To summarize the above, Pn=Txpn-1
+Pn-1+An Txpn=f(Pn) AFP=Txpn+Pn+An.

After performing the calculation in S324 or S327, in S325, the flag C10 is set to 0, and in the next distance measurement, the current calculation is handled as the first calculation after correction. Also, in S326, the flag BOV
= 0.

In FIG. 7, S221 and S223 are both cases where the subject is moving from near to far. When the subject moves away from the camera at a constant speed, the subject image speed gradually slows down.
The amount of lens drive decreases accordingly. In this case, if correction is performed in advance by the release time lag, as in the case where the subject is approaching the camera, there is a high possibility that over-correction will occur. If over-correction occurs, it will result in so-called back focus, which is not very desirable when considering the quality of the photo. Therefore, when the subject moves in a direction away from the camera, the camera basically follows the subject without moving in advance by the release time lag.

FIG. 18 is a graph showing the relationship between the subject image position of a subject moving away from the camera and the lens drive pulse. In FIG. 18, the number of motor drive pulses obtained at point ■ is assumed to be A1. It is assumed that after this, a pulse A1 is applied to the motor to drive the lens, and after a time t1 has elapsed, the number of pulses A2 at point ■ is determined. The amount of movement of the subject image from point 2 to point 2 becomes A2 when converted into the number of pulses. Therefore, the object image movement speed OBJsp between the points ■ and ■ points is OBJsp=A2/t1. Here, the subject image position at point ■ after time t2 has elapsed from point ■ based on the subject image position at point ■ is expressed as A2+t2×OBJsp, assuming that the subject image speed is constant. Here, time t2 is considered to be the same as t1 as explained in the proactive tracking section, so t
The amount of movement of the subject image between A2 and A2 is considered to be the same. Therefore, the driving amount is calculated to be 2×A2. In other words, the point where the motor is driven by 2×A2 at point ■ coincides with the subject image position after time t2 has elapsed. In this case, even if you interrupt the release ON after the lens drive ends and start exposure after the release time lag has elapsed, the focus position is in front of the subject image position at that point and is not in the rear focus state, so do not calculate TXP. Perform follow-up. As a result of driving the lens by 2×A2 based on the defocus amount A2 obtained at point ■, the result is A at point ■.
Assuming that a defocus amount of 3 is obtained, the next drive amount is simply set to A3×2 as in the previous drive without performing any correction as in proactive tracking. That is, the following formula can be obtained as a general formula for determining the amount of lens drive during rear tracking. Lens drive amount AFP=2×An (However, assume that t1=t2 and the lens was driven last time.)

FIGS. 19 and 20 show S223 in FIG. 7, respectively.
, represents the subroutine of S221.

In FIG. 19, in S271, the movement amount (number of pulses) XX of the subject image and the amount of defocus (number of pulses)
The lens drive amount is calculated by adding . The movement amount XX of the subject image is calculated in S206 to S209 of FIG. 7 based on whether or not the lens was driven last time, and XX=An if the lens was driven last time, and XX if it was not driven last time. =An-An-1, and the lens drive amount AFP calculated in S271 of FIG. 19 does not exceed 2×An.

In FIG. 20, the current defocus direction is checked in S272. This is because even though the subject is moving away, if the defocus direction after driving the lens is positive, that is, if the rear focus is on, over-compensation is being performed, so we check to avoid this. It is something. In case of over correction, S2
At step 77, the correction is turned off, the calculation data is cleared, and the current data is recalculated as the first AF data. If the check to see if over-correction is passed, in the next S273 to S275, S206 to S20 in FIG.
9, the amount of subject movement is calculated based on the presence or absence of the previous lens drive, and the lens drive amount AF is calculated in S276.
Set P. This is similar to the case in FIG.

Here, the determination of focus in S6 of FIG. 3 will be explained. This determination is made based on whether the defocus amount obtained in S2 is within the aforementioned predetermined focusing width. However, in advance tracking mode, control is always performed to advance by the amount of the release time lag, so even if it is possible to focus after the release time lag has elapsed, the defocus amount may not be within the focus range when measuring distance. do not have. Furthermore, even if the object is within the focus range during distance measurement, it does not necessarily mean that the object will be within the focus range after the release time lag has elapsed. Therefore, from the obtained defocus amount itself, focus cannot be detected even if it is in a focusable state. Therefore, Figure 7
In step S217, the defocus amount for focus check is calculated. This recalculation in S217 will be explained with reference to FIG. 23. First of all, in S51, the previous AF
Movement amount Txpn- for release time lag in processing
1 is converted from the number of pulses to the image plane defocus amount DD. Next, in S52, the image plane defocus amount DD is added to the defocus amount Defocus obtained by the current distance measurement, regardless of whether it is positive or negative, to obtain the defocus amount for focus check. In addition, in the case of follow-up,
Since the lens is not driven extra by the release time lag, such calculation of the defocus amount for focus checking is not performed.

With the above operation, when the subject is moving toward the camera, the lens is driven in advance by the release time lag, so it is difficult to know when to turn on the release.
However, the focus will not be too far behind, and you can always take pictures with the camera in focus. Furthermore, if the subject is moving away from the camera, the algorithm follows the subject, so it is possible to take a photograph in focus without over-compensating and getting the subject behind the camera.

[0068] In distance measurement, if the integration time is shortened, the sampling interval of the distance measurement data can be shortened, and it becomes easier to follow the subject, so a limit may be set on the integration time. FIG. 21 is a flowchart in the case of setting a limit on the integration time. Usually, the maximum value of integration time Ti
ntMAX = normal maximum integration time NORMAX, but when the correction is ON, as shown in Figure 21, by using the maximum integration time CONMAX when the correction is ON, which is smaller than the normal maximum integration time NORMAX, as the maximum value of the integration time. Distance measurement can be performed with a shorter integration time.

Furthermore, as described above, there may be cases where the lens is driven to an end point during tracking. When driving the lens, the end point detection circuit 11 (FIG. 1) is reset in S15 of FIG. 3, and the INT2 interrupt is enabled. The end point detection circuit 11 generates an interrupt at INT2 of the CPU 3 when no pulse is received from the encoder for a certain period of time. That is, when the lens is driven to the end point while the lens is being driven, the encoder 5 no longer outputs pulses, so the end point detection circuit 11 is turned on and an INT2 interrupt occurs. FIG. 22 is a flowchart of this interrupt processing. When an interrupt occurs, lens driving is stopped, subsequent end point detection interrupts are prohibited, and then correction is turned OFF (
S501-503).

If no interrupt occurs and lens driving is completed, the INT2 interrupt is prohibited in S16-3 of FIG.

FIG. 24 is a subroutine showing an example of the focusing process shown in S7 of FIG. 3. By lighting the focusing LED by the LED drive circuit 10 of FIG. This is to let you know that you are in a state of focus. This focusing LED is preferably provided within the viewfinder of the camera. Here, if C10 is not 1, the process simply displays the focus and returns.

[0072] Furthermore, when C10=1, that is, when proactive tracking is performed, MAX AFPspeed/Kva
lue≧OBJSP(mm/s)
MAX AFPspeed: Maximum drivable speed (pulses/s) OBJSP: In-focus display is always performed when the object image speed (mm/s) is reached. In other words, when the focus is displayed during proactive tracking, you can confirm that you can always take in-focus photos (at MAX in the flow chart).
S=MAX AFPspeed/Kvalue, OB
J=OBJSP).

[0073] When the subject speed exceeds the tracking limit speed, that is, MAX AFPspeed /Kv
When alue<OBJSP (mm/s) holds, it is not possible to advance by the amount of the release time lag, and even if the shutter is released, it is not possible to take a photograph in focus, so in this case, the focus is not displayed.

In addition, in the case of advance tracking mode, the AF switch is set in advance by the release time lag.
If only 1 is turned on to bring the camera into focus, and then the release switch SWR is turned on at the end of lens driving, the subject image position and the focus position will always match at the start of exposure. However, the release switch is pressed at any other time.
If the release switch SWR is turned on at the same time as the AF switch SW1 and the release ON interrupt is permitted after a predetermined processing time has elapsed after the lens is driven, the starting point of the release time lag assumed in advance and the actual The release ON interrupt timings do not match. Further, in the case of tracking, the release time lag is not taken into consideration. Therefore, in these cases, the subject image position and the focus position do not necessarily coincide at the start of exposure. Therefore, if the lens is configured to be driven as much as possible during the release time lag, more precise focusing can be achieved. Furthermore, when taking several pictures in succession in advance tracking mode, the tracking ability cannot be improved if the AF is restarted after the mirror has been lowered and the film has been advanced after exposure. Since distance measurement is possible after the mirror is lowered, distance measurement is started immediately after the mirror is lowered, and regardless of whether winding is completed or not, the number of drive pulses based on the distance measurement data and the measurement obtained before the release are The tracking ability can be improved by driving the lens by adding the number of driving pulses depending on the distance.

FIG. 25 is a flowchart of release interrupt processing taking these cases into consideration, and FIGS. 26 and 27
FIG. 3 is a diagram showing the state of lens driving controlled by this flowchart. Figure 26 shows the release ON when the lens is stopped.
FIG. 27 shows a state in which a release ON interruption occurs during lens drive. The release ON interrupt is enabled in S8 of FIG. 3, and this process is started by interrupting the release ON signal from the release switch SWR. First, S601
, control the mirror up and lens aperture, and
In 602, it is determined whether correction is ON. Correction O
In the case of FF, normal release control of S603 to S605 is performed via S602. That is, the shutter is controlled in S603, the mirror is finished lowering in S604, and then the shutter is controlled in S604.
At 05, winding is performed and the interrupt processing is ended. On the other hand, when the correction is ON, it is determined in S607 whether or not the lens is being driven, and based on the result, S608 or
In step 609, the lens drive amount AFP is reset. If the lens is not being driven, in S608, the amount of movement of the subject since the end of the previous lens drive is calculated using the elapsed time tt since the end of the previous lens drive, as shown in FIG. 26, using the formula: OBJSP×KVALUE× tt and newly set the value to AFP. On the other hand, if the lens is being driven, in S609, the driving amount to be driven during the elapsed time tt from the end of the previous lens driving as shown in FIG.
The new lens drive amount AFP is calculated by subtracting AFP-Dar (where Dar: remaining lens drive amount), which is the already driven portion of the current lens drive setting value AFP, from ×tt.
shall be. A reset in S608 or S609
If FP exceeds the maximum number of AF pulses MXM that can be driven in the release time lag time, in S611, AFP=M
Let it be XM. The lens is driven by the set AFP and exposure is performed (S612, S613).

When it is determined in S614 that the mirror has finished lowering, the next distance measurement, that is, the integration and
Input and calculation are performed in S615, and the number of drive pulses An is calculated in S616.

Now, referring to FIG. 28, a description will be given of a function that increases the tracking ability by starting the next tracking operation as soon as distance measurement becomes possible after the shutter release is completed. That is, in the tracking mode, if the next distance measurement, calculation, etc. are started after the film has been wound up after the release, the tracking ability cannot be improved. Since it is possible to measure the distance when the mirror is lowered, the distance measurement is started after the time t0 when the mirror was raised last time, the release operation is started at t1, and the distance measurement is started at the time t11 when the mirror has finished lowering. Then, the number of driving pulses An is determined. Then, the number An-1 of drive pulses determined before the previous distance measurement, that is, the start of the release operation, is added to the number An of drive pulses to obtain a new number of drive pulses. By configuring in this manner, the time t2 is shorter than when the mirror is lowered and the film winding is completed until t2, and then the next distance measurement is started and the lens is driven (in the case shown by the dotted line in FIG. 28). The follow-up operation can be continued earlier by the time -t11 (in the case represented by the solid line in FIG. 28). Then, in S617, the previous defocus amount An-1+the current defocus amount An=AFP, and in S618, the flag A1S is cleared, the correction is turned OFF, and the release interrupt processing is ended. After the interrupt ends, the process moves to LMOV in FIG. 3, and the lens is driven by the above-mentioned driving amount AFP.

FIG. 29 is a flowchart showing a series of so-called overlap processes in this embodiment. The overlap process further performs a distance measurement operation while the lens is being driven to more accurately determine the position of the focusing lens. When distance measurement is performed on a subject that is significantly deviated from the focus position at the time of initial distance measurement, the obtained defocus amount itself contains a large error, so the determined lens drive amount may not be an accurate value. Therefore, the focusing operation will not be satisfactory. Therefore, by configuring the camera to further calculate the drive amount while the lens is being driven, overlap processing is performed in order to perform accurate focusing operation.

First, CCD integration is started while the lens is being driven. The lens drive amount is set in the counter 6,
In S701, the number of lens drive pulses at the start of integration is set to C1, and the number of lens drive pulses at the end of integration is set to C3. In S702, the CCD integral data is input, and in S70
In step 3, the amount of defocus is calculated. S7
In step 04, based on the obtained defocus amount, the number of AF pulses is calculated in the same manner as in the process of S3 in FIG. 3, and the calculated value is set as Cx. The number of lens drive pulses in the counter 6 at the time of Cx calculation is assumed to be C4. In S705, the number of lens drive pulses required to update the lens drive amount is calculated using the following equation. C2=(C1+C3)/2 A=Cx-(C4-C2) The above A is the updated number of lens drive pulses. This is set in counter 6 in S706, and the process ends.

Note that, as is clear from S17 and S18 in FIG. 3, overlap processing is not performed when the correction is ON, that is, in the tracking mode. As mentioned above, overlap processing is necessary when the amount of defocus is large, but when the correction is ON, the focusing lens is tracking the subject, so it is difficult to imagine that the amount of defocus is that large. This is because it is unthinkable. Additionally, the problem arises that the AFP value obtained for tracking is updated by AFP calculation for overlap processing, which is performed in a routine different from the main routine, making it impossible to perform the tracking operation itself. It is.

[0081] In the automatic focus adjustment device installed in the camera configured as detailed in the above embodiment,
When the subject's image plane is moving at a predetermined speed or higher, it enters tracking mode, and when the subject is approaching the camera, it follows the subject in advance by the release time lag, and on the other hand, when the subject is moving away, it follows the subject in advance by the release time lag. The focusing lens is controlled to follow the target. Moreover, the next distance measuring operation for the subject is started after a predetermined period of time, for example, the mirror lowering completion time, without waiting for the time required for the release interrupt operation to elapse. Therefore, it is possible to always quickly follow a continuously moving subject, and it is possible to continue taking photographs with appropriate focus.

[0082] Furthermore, by setting the number of times the speed of the subject image is measured to determine whether to enter the tracking mode to a predetermined number of times or more, it is possible to enter the tracking mode after accurately grasping that the subject is moving. It is also possible to configure

Furthermore, even if the focusing lens is already within the in-focus range and the in-focus display is being performed, if the tracking mode is in progress, the lens will be driven further to achieve complete focus. It is also possible to configure

The release time lag used in calculations for tracking may not be used as is, but a value that takes into account the integration time for distance measurement may be used, thereby allowing smoother tracking.

In addition, if the release is not turned on immediately after the lens drive ends, the amount of defocus can be further reduced by configuring the lens to drive the focusing lens by an amount that can be driven within the release time lag. It is also possible to make it smaller.

Furthermore, in the case of the tracking mode, it is also possible to perform a focus display such as lighting an LED only when the object is in focus and tracking is possible. In this case, it is preferable to make the lighting of the LED visible in the viewfinder of the camera. With this configuration, the camera has an indicator function that notifies the operator that the camera is in focus.

In this embodiment, the tracking mode is entered when it is determined in two distance measurements that the moving speed of the image plane of the subject is equal to or higher than a predetermined speed. However, the configuration may be such that the tracking mode is entered when the determination is made a predetermined number of times or more. Additionally, if the amount of lens drive during tracking is equal to or greater than a predetermined value three or more times, it is determined that tracking is not being performed correctly and tracking is turned off. It is possible to set.

Furthermore, if the integration/calculation time becomes long, there is a possibility that the lens drive will not be able to follow the moving speed of the object, so by setting an upper limit on the integration time in the tracking mode, the distance measurement time can be shortened. , it can be followed smoothly.

[0089] If the moving speed of the subject is high and the amount of lens drive is relatively large accordingly, overlap processing may be necessary, but normally during tracking mode,
The amount of lens drive is relatively small, and if the amount of lens drive becomes relatively large even though it is in tracking mode, it is considered that the moving speed of the subject is close to the limit value that can be tracked. Therefore, by configuring so that overlap processing is not performed during the follow-up mode, appropriate follow-up driving can be realized.

Furthermore, although this embodiment has been described only in the so-called release priority mode in which the release operation is performed after the in-focus state is achieved, the so-called shutter priority mode in which the release operation is performed regardless of the in-focus state is described. It is also applicable to cases where That is, the configuration is such that either shutter priority or release priority can be selected using a switch (not shown), and in the case of shutter priority, step S in FIG.
If 6-1 and S8 are jumped, the release operation will be performed regardless of the in-focus state.

[0091]

Effects of the Invention The automatic focusing device according to the present invention includes a focusing lens movable in the optical axis direction, a distance measuring means for determining the defocus amount of the focusing lens with respect to a specific subject, and a distance measuring means for determining the defocus amount of the focusing lens with respect to a specific subject. calculation means for calculating the relative movement direction and movement speed of the specific subject in the optical axis direction based on the plurality of defocus amounts obtained by the means; The distance measuring means includes a drive control means for driving the focusing lens to a position where the specific subject moves to a focused position after the elapse of time, and a release means for performing an exposure process. When the release operation starts, the distance measurement operation starts after a certain period of time and before the release operation ends, so even if the specific subject moves, appropriate focusing processing is performed, so you can always take photos that are in focus. In addition, in the focus adjustment process after the start of the release, instead of starting distance measurement for the next calculation after the release operation is all completed, it is possible to adjust the focus at a certain point during the release operation, for example, Since distance measurement is started when the mirror has finished lowering, and the data is used for the next calculation, continuous and appropriate automatic focus adjustment can be performed, especially when in continuous shooting mode.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main parts of an AF system of an automatic focus adjustment device of the present invention.

FIG. 2 is a graph explaining the basic principle of the tracking method of the present invention.

FIG. 3 is a flowchart representing an embodiment of processing of an AF system that employs the tracking method of the present invention.

FIG. 4 is a graph illustrating the principle of changing the mode from trailing tracking to proactive tracking in this embodiment.

FIG. 5 is a graph illustrating a calculation method during proactive tracking according to the present embodiment.

FIG. 6 is a graph illustrating the principle of moving object prediction calculation in consideration of integration time in this embodiment.

FIG. 7 is a main flowchart of a moving object prediction calculation according to the present embodiment.

FIG. 8 is a flowchart illustrating calculations when a subject approaches the camera immediately after correction is turned on in this embodiment.

[Fig. 9] In this embodiment, the second and subsequent times after the correction is turned on,
12 is a flowchart illustrating calculations when a subject approaches a camera.

FIG. 10 is a graph illustrating a moving object prediction calculation based on the movement status of the subject and the driving result of the lens in this embodiment.

FIG. 11 is a graph illustrating a moving object prediction calculation based on the movement status of the subject and the driving result of the lens in this embodiment.

FIG. 12 is a graph illustrating a moving object prediction calculation based on the movement status of the subject and the driving result of the lens in this embodiment.

FIG. 13 is a graph illustrating a moving object prediction calculation based on the movement status of the subject and the driving result of the lens in this embodiment.

FIG. 14 is a graph illustrating a moving object prediction calculation based on the movement status of the subject and the driving result of the lens in this embodiment.

FIG. 15 is a graph illustrating a moving object prediction calculation based on the movement status of the subject and the driving result of the lens in this embodiment.

FIG. 16 is a graph illustrating a moving object prediction calculation based on the movement status of the subject and the driving result of the lens in this embodiment.

FIG. 17 is a graph illustrating a moving object prediction calculation based on the movement status of the subject and the driving result of the lens in this embodiment.

FIG. 18 is a graph illustrating an algorithm when the subject moves away from the camera in this embodiment.

FIG. 19 is a flowchart illustrating calculations when the subject moves away from the camera immediately after correction is turned on in this embodiment.

FIG. 20 is a flowchart illustrating calculations when the subject moves away from the camera from the second time onwards after the correction is turned on, according to the present embodiment.

FIG. 21 is a flowchart illustrating an example of processing when a limit is set on the integration time.

FIG. 22 is a flowchart showing processing when an end point of a lens is detected during tracking according to the present embodiment.

FIG. 23 is a flowchart showing a focus check defocus amount recalculation subroutine for checking whether the position where the lens is driven is the in-focus position based on the moving object prediction calculation.

FIG. 24 is a flowchart illustrating in-focus display during subject tracking in this embodiment.

FIG. 25 is a flowchart illustrating an example of processing when distance measurement is performed immediately after the mirror is lowered in continuous shooting.

FIG. 26 is a graph explaining the operation of the flowchart shown in FIG. 25;

FIG. 27 is a graph explaining the operation of the flowchart shown in FIG. 25;

FIG. 28 is a graph explaining the operation of the flowchart shown in FIG. 25;

FIG. 29 is a flowchart illustrating overlap processing in this embodiment.

FIG. 30 is a graph explaining a conventional AF system.

FIG. 31 is a graph explaining a conventional AF system.

FIG. 32 is a graph explaining a conventional AF system. 1 Distance sensor (distance measurement means) 3 CPU (calculation means) 8 Release control circuit

Claims (3)

[Claims] 1. A focusing lens movable in the optical axis direction, a distance measuring means for determining a defocus amount for a specific subject by the focusing lens, and a plurality of defocus amounts determined by the distance measuring means. calculation means for calculating the relative movement direction and movement speed of the specific subject in the optical axis direction based on the calculation means; a drive control means for driving the focusing lens to a position where it is in focus with respect to a position, and a release means for performing exposure, and the distance measuring means is configured such that the release means starts a release operation. An automatic focus adjustment device characterized in that when a specific time period has elapsed, a distance measuring operation is started before the release operation ends. 2. In claim 1, the release means includes a movable mirror, and the specific time is a time required for the mirror that has been raised to come down from the start of the release operation of the release means. Automatic focus adjustment device. 3. The drive control means according to claim 1, based on the amount of addition of the drive amount based on the distance measurement performed before the end of the release operation and the drive amount based on the previous distance measurement of the distance measurement. An automatic focus adjustment device characterized by driving a lens after a release operation is completed.