JPH05107455A - Focusing device - Google Patents

Abstract

PURPOSE:To provide a focusing device which can surely catch a moving subject which has been followed before exposure after the exposure and drive a photographing lens. CONSTITUTION:A predicted defocusing amount calculating means 106 calculates a predicted defocusing amount for a moving subject which has been followed before exposure at a first focus detection point after the exposure, and a following driving amount calculating means 103 calculates a following driving amount to make a photographing lens follow the moving subject without delay based on the defocusing amount which is the closest to the predicted defocusing amount among a plurality of defocusing amounts detected in a plurality of focusing detection zones at the same point of time and an image surface moving speed of the moving subject detected before the exposure for driving the photographing lens to surely catch the identical subject both before and after the exposure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus adjusting device for tracking and driving a photographing lens on a moving subject.

[0002]

2. Description of the Related Art From a plurality of focus detection areas set in a shooting screen, a focus detection area closest to the current focus point of a shooting lens, that is, a focus detection area with a minimum defocus amount is selected. Based on the defocus amount detected in the detection area, the tracking drive amount for tracking the shooting lens with respect to the moving subject without delay is calculated, the shooting lens is driven, and when the shutter is released, the image is taken during exposure. 2. Description of the Related Art There is known a focus adjusting device that corrects a tracking drive amount and drives a photographing lens so that the lens focuses on a moving subject.

FIG. 3 is a diagram showing a locus of image plane positions of a moving main subject and a background subject, and a locus of positions of photographing lenses. During the tracking drive, three basic operations of charge accumulation (I) of a photoelectric conversion element such as CCD, focus detection calculation (C) based on output data of the photoelectric conversion element, and lens drive (D) based on the focus detection result are repeated. Then, the photographing lens is driven to follow the moving subject. When the shutter is released, the taking lens is driven so as to focus on the moving subject at the time of exposure at time t1, and when the exposure is completed, the basic operation is restarted again.

[0004]

However, in the conventional focus adjusting apparatus, as shown in FIG. 3, for example, when there is a background subject that moves at a speed substantially similar to that of the main subject, focus detection after exposure ( At the time of I), the focus detection area closest to the current focus point of the taking lens, that is, the focus detection area with the smallest defocus amount is selected, and the tracking drive is performed based on the defocus amount of the detection region. At the time of first focus detection after exposure, the focus of the photographing lens is adjusted with respect to the background subject having a defocus amount smaller than that of the main subject, and the background subject is tracked thereafter.

It is an object of the present invention to provide a focus adjusting device which accurately captures a moving object which has been tracked before the exposure even after the exposure and drives the photographing lens for tracking.

[0006]

The present invention will be described with reference to FIG. 1, which is a claim correspondence diagram. According to the present invention, a plurality of focus detection areas are provided in a photographing screen, and each focus detection area is photographed. A focus detection unit 100 that repeatedly detects the defocus amount indicating the focus adjustment state of the lens, and a stationary movement that determines whether the subject is stationary or moving based on at least the current and past defocus amounts detected by the focus detection unit 100. Judgment means 101 and at least focus detection means 1
Image plane moving speed calculation means 102 for calculating the moving speed of the object image surface formed by the photographing lens based on the current and past defocus amounts detected in 00, and the movement of the object by the stationary movement determination means 101. Is determined, the minimum defocus amount among the plurality of defocus amounts detected by the focus detection unit 100 and the image plane moving speed calculation unit 1
A tracking drive amount calculation means 103 for calculating a tracking drive amount for tracking the photographing lens with respect to a moving subject without delay based on the image plane moving speed calculated in 02, and exposure when the shutter is released. Sometimes the correction means 104 corrects the tracking drive amount calculated by the tracking drive amount calculation means 103 so that the photographing lens focuses on the moving subject, and the tracking drive amount or correction means 104 calculated by the tracking drive amount calculation means 103. The present invention is applied to a focus adjusting device provided with a driving unit 105 that drives a taking lens according to the tracking drive amount corrected in. Then, based on the image plane moving speed of the moving subject calculated by the image plane moving speed calculating means 102, a predicted defocus amount for calculating a predicted defocus amount of the photographing lens for the moving subject at the time of first focus detection after exposure. The tracking drive amount calculation unit 103 includes a calculation unit 106, and the tracking drive amount calculation unit 103 uses the predicted defocus amount calculation unit 106 among the plurality of defocus amounts detected by the focus detection unit 100 only at the time of first focus detection after exposure. The defocus amount closest to the calculated predicted defocus amount, and the image plane moving speed calculation unit 102.
The above-described object is achieved by calculating the tracking drive amount for tracking the taking lens with respect to the moving subject without delay based on the image plane moving speed calculated in step S4.

[0007]

The tracking drive amount calculation means 103 predicts the defocus amount calculation means 1 among the plurality of defocus amounts detected by the focus detection means 100 at the time of the first focus detection after exposure.
In order to cause the moving lens to track the photographing lens without delay based on the defocus amount closest to the predicted defocus amount calculated in 06 and the image plane moving speed calculated by the image plane moving speed calculating unit 102. The tracking drive amount of is calculated. As a result, it is possible to accurately capture the moving subject that was being tracked before the exposure even after the exposure.

[0008]

FIG. 2 shows the structure of a camera according to an embodiment. A part of the light flux from the subject 2 that has passed through the photographing lens 1 is reflected by the main mirror 3 and is observed by the photographer via the pentaprism 4 and the eyepiece lens 5. On the other hand, the other part is transmitted through the main mirror 3, reflected by the sub mirror 6, and guided to the AF module 7. AF module 7
Is a well-known focus detection optical system, performs photoelectric conversion by a signal from the CPU 8, and further outputs the photoelectric conversion output as CP.
Transfer to U8. The CPU 8 executes a control program described later to perform focus adjustment control. Lens information memory 9
Transfers lens information such as the focal length of the photographing lens 1 and the conversion coefficient between the defocus amount and the lens drive amount to the CPU 8 in response to a signal from the CPU 8.

The AF motor 10 is activated by a signal from the CPU 8 and drives the drive mechanism 11 of the taking lens 1 via the coupling 12. Further, the encoder 13 uses the AF
An encoder pulse corresponding to the rotational position of the motor 10 is sent to the CPU 8. The display 14 displays the alignment state of the taking lens 1. When the release switch SW2 is turned on, the mirror control circuit 15 controls up and down of the main mirror 3 by a signal from the CPU 8. When the mirror up is completed, the shutter control circuit 16 runs the shutter to complete the exposure. After the exposure is completed, the mirror down is performed by the mirror control circuit 15. The release switch SW1 is
The switch is a switch that is turned on when the shutter release button is pressed halfway, and the release switch SW2 is a switch that is turned on when the shutter release button is fully pressed.

FIG. 4 is a flowchart showing the main program. The operation will be described with reference to this flowchart. The CPU 8 starts execution of this main program when a main SW (power supply) (not shown) is turned on. In step S401 after the start of execution, various flags and variables necessary for the program are initialized. For example, the focus adjustment mode is set to the one-shot mode (hereinafter, also referred to as S mode). The one-shot mode is a focus adjustment mode in which the taking lens 1 is driven when the shutter release button is pressed halfway and the lens driving is stopped once the subject is in focus. Next, in step S402, it is determined whether or not the shutter release button is half-pushed by the release switch SW1. If half-pushed, the process proceeds to step S403, and if not, the process returns to step S401. Step S403
Then, the CCD accumulation control subroutine shown in FIG. 5 is executed.

CCD accumulation control will be described with reference to the flowchart of FIG. In step S501, it is determined whether or not the taking lens 1 is currently being driven. If it is being driven, the process proceeds to step S502, and if it is not being driven, step S50.
Go to 3. In step S502, it is determined whether or not scanning is in progress. If scanning is in progress, the process proceeds to step S503. If not, the process returns to step S501 to wait until the lens driving is finished, and after the lens driving is finished, the process proceeds to step S503. .. In step S503, the previous accumulation time ITn is stored in ITn-1, and the current value of the free running timer AFT1 is substituted into the variable ITn. Further, the variables TEn and TEn-1 representing the focus detection time interval are calculated and stored. In step S504, 1 after release
Whether or not it is the first focus detection is determined. If it is the first focus detection, the process proceeds to step S506, and if not, the process proceeds to step S505. In step S505, the previous focus detection interval TEn is stored in the variable TEN representing the standard time for performing the predictive driving. This variable TEN is used as a parameter of time for predictive driving when the release is not made.

In step S506, the lens position ECNT at the start of accumulation is substituted into the variable PLC1. In a succeeding step S507, a charge accumulation start signal is sent to the CCD of the AF module 7. In step S508, it is determined whether or not the accumulation is completed, and when the accumulation is completed, the process proceeds to step S509,
It is determined whether or not the scan is currently being performed. If scanning is in progress, the process proceeds to step S510, and if not, the process returns to the main program in FIG. In step S510, the lens position ECNT at the end of the accumulation is substituted into the variable PLC2, and in the following step S511, the variables PLC1 and PL1 are set.
After calculating the lens position PLC of the accumulation center by C2,
The accumulation control of the CCD is terminated and the process returns to the main program of FIG.

Returning to the main program of FIG. 4, in step S404, the output from the CCD is A / D converted and stored in the memory. Next, in step S405, information regarding the lens is acquired from the lens information memory 9. Then, in step S406, the defocus calculation subroutine shown in FIG. 6 is executed.

The calculation process of the defocus amount will be described with reference to the flowchart of FIG. In step S601, based on the output data of the CCD stored in the memory, the defocus amount DFa,
DFb and DFc are calculated. In step S602, it is determined whether or not focus detection is not possible in all areas. If all are undetectable, the process proceeds to step S619 and at least 1
If focus detection is possible in one area, the process proceeds to step S603. In step S603, it is determined whether or not it is the first time after the shutter release button is half-pressed. If it is the first time, the process proceeds to step S618, and if not, the step S60.
Go to 4. In step S604, it is determined whether or not it is the front turning body. If it is a moving body, the process proceeds to step S605, and if not, the process proceeds to step S615. Step S60
In step 5, it is determined whether or not it is the first focus detection after the shutter release, and if it is the first time, the process proceeds to step S606 to calculate the predicted defocus amount during distance measurement, and if not, the process proceeds to step S617.

In step S606, the predicted defocus amount DFes during distance measurement is calculated by the following equation. DFes = Sn × TS (1) Here, Sn is the image plane moving speed, and TS is the time interval from the exposure to the current focus detection. If the exposure time is short, TS is about 100 to 150 msec in a substantially constant time. Therefore, the TS may calculate DFes using a constant value without measuring the time interval with the timer. But,
If the exposure time is long, it must be measured by a timer. In step S607, the absolute value of the difference from the estimated distance measurement defocus amount DFes of each area is calculated, and ΔDF is calculated.
a, ΔDFb, and ΔDFc. Step S608
Then, the defocus amount of the smallest area of ΔDFa, ΔDFb, and ΔDFc is stored in DFn.

In step S609, it is determined whether or not focus detection is not possible this time. If it is not possible, the process returns to the main program of FIG. 4, otherwise step S610.
Go to. In step S610, a counter COUNT for determining whether or not the number of times of focus detection required for the prediction calculation is reached.
Is incremented. In step S611, it is determined whether or not scanning is currently performed because focus detection is impossible. If scanning is in progress, the process proceeds to step S612, and if not, the process returns to the main program in FIG. In step S612, since the focus can be detected this time, the scan flag is cleared to stop the scan. In a succeeding step S613, the AF motor 10 is stopped. In step S614, charge accumulation and focus detection calculation are performed while driving the taking lens 1, so the defocus amount in which the lens drive amount during the accumulation calculation is corrected is calculated by the following equation. DFn = DFn + (ECNT-PLC) / (KB × KL) (2) where KB is the number of pulses generated by the encoder 13 per one rotation of the coupling, and KL is the coupling rotation per unit lens driving amount. The number, ECNT, is a pulse count that indicates the current relative lens position. Here, the lens position of the center of charge accumulation is set as the midpoint of the lens positions of the start and end of the accumulation, but the lens position may be stored and the center may be obtained by a constant timer interruption during the accumulation.

In step S615, it is determined whether or not the subject is in focus, and if the subject is in focus, the process proceeds to step S617 so that the current status has priority. If the subject is not in focus, the closest priority is given to step S616. Go to. In step S616, the area showing the closest defocus amount is selected,
Store in DFn. In step S617, 0 is stored in the predicted defocus amount DFes during distance measurement. Step S6
At 18, the COUNT is initialized to 0 because it is the first focus detection after the shutter release button is half-pressed. Step S
At 619, the low-con flag is set because it cannot be detected in all areas.

Next, returning to the main program of FIG. 4, in step S407, the moving body determination subroutine shown in FIG. 7 is executed. Here, the moving body determination process will be described with reference to the flowchart shown in FIG. 7. In the moving body determination subroutine, it is determined whether the subject is a moving body or is still. In step S701, it is determined whether or not scanning is in progress. If scanning is in progress, the process proceeds to step S717, and if not, the process proceeds to step S702. This is because the moving body determination is not performed immediately after scanning. Step S702
Then, it is determined whether or not the focus cannot be detected. If the focus cannot be detected, the process proceeds to step S714. If not, the process proceeds to step S7.
Go to 03. In step S703, it is determined whether or not the drive direction has been inverted by the previous lens drive. If the drive direction has been inverted, the process proceeds to step S717, and if not, the process proceeds to step S704. This is the drive mechanism 11 during reverse driving.
This is to avoid erroneous determination of stationary / moving due to the backlash.

In step S704, the previous image plane movement amount P
n is stored in Pn−1, and in the subsequent step S705, COUNT
It is determined whether T is larger than 1. If it is larger than 1, the process proceeds to step S706, and if not, step S7.
Proceed to 17. This is performed to determine whether or not there is focus detection data necessary for calculating the image plane movement amount. In step S706, the image plane movement amount Pn during focus detection is calculated by the following equation. Pn = DFn + DR-DFn-1 (3) Here, DR is the lens drive amount during focus detection. In step S707, it is determined whether Pn and Pn-1 have different signs. If they have different signs, the process proceeds to step S718, and if not, the process proceeds to step S708. This determination is to avoid accidentally entering the tracking mode due to camera shake or the like.

In step S708, it is determined whether or not it is the front rotating body. If it is the front rotating body, the process proceeds to step S710, and if it is stationary, the process proceeds to step S709. This is to prevent hunting in moving object determination so as not to immediately exit the tracking mode once it is determined to be a moving object. In step S709, it is determined whether or not the sum of the previous image plane movement amount Pn-1 and the current image plane movement amount Pn is larger than a predetermined value δ2. If it is larger, the process proceeds to step S711, and if it is smaller, the process proceeds to step S718. .. In step S710, it is determined whether or not the sum of the previous image plane movement amount Pn-1 and the current image plane movement amount Pn is larger than a predetermined value δ1, and if it is larger, the process proceeds to step S711, and if it is smaller, step S718.
Go to.

In step S711, the previous image plane movement amount P
A ratio between n-1 and the current image plane movement amount Pn is calculated. If the ratio is within a predetermined range, it is determined that the subject is a moving body and the process proceeds to step S712. If it is outside the predetermined range, step S71 is performed.
Go to 8. This is to prevent the subject from changing when the composition of the camera is changed, and to prevent the subject change from being erroneously determined as the movement of the subject. The predetermined values δ1 and δ2
Takes a value of 50 μm to 200 μm and has a relationship of δ1 ≦ δ2. In step S712, the moving object flag is set because it is determined to be a moving object in the above-described determination, and in the following step S713, the image surface moving speed Sn is calculated from the image surface moving amount Pn and the time interval TEn, and the main program of FIG. Return to.

In step S714, it is determined whether or not it was the previous low-con, and if it was the previous low-con, step S7.
If not, the process proceeds to step S715.
This is to prevent the moving object from being determined when the low contrast is obtained twice in a row. In step S715, it is determined whether or not it is the front rotating body. If it is the front rotating body, the process proceeds to step S716, and if not, the step S717.
Go to. This is likely to be a moving object even if it was the front rotating body, but it is possible that the object has been missed from the distance measurement area due to the movement of the object, so do not perform the normal low contrast operation. This is because. Step S7
In 16, the image plane movement amount is indefinite because of the low contrast this time, but in most cases, the image plane movement amount does not change, so the previous image plane movement amount is used as the current image plane movement amount. In step S717, 0 is stored because the image plane movement amount is indefinite. In step S718, since it is determined that the subject is a still subject, the moving body flag is cleared.

Returning to the main program of FIG. 4, the focus determination routine shown in FIG. 8 is executed in step S408.
The focus determination process will be described with reference to the flowchart shown in FIG. In step S801, it is determined whether the focus cannot be detected. If the focus cannot be detected, the process proceeds to step S1001 in FIG. 10, and if not, the process proceeds to step S802. In step S802, the scan prohibition flag is set. This is to prevent scanning once focus detection becomes possible. In step S803, it is determined whether or not it is a moving body, and if it is a moving body, step S804.
Otherwise, to step S808. In step S804, the focus detection mode MODE is set to continuous mode (hereinafter, also referred to as C mode).
The continuous mode is a focus adjustment mode in which the taking lens 1 is continuously driven so that the subject is always in focus while the shutter release button is half-pressed.

In step S805, the release permission flag is set to permit the release, the focus lock flag is cleared, the focus flag is cleared, and the release switch SW2 interrupt is permitted. Continued Step S8
At 06, the subroutine of tracking operation 1 shown in FIG. 9 is executed to perform the prediction drive.

In step S901 of FIG. 9, it is determined whether or not the lens has been driven last time, and if it is driven, step S90.
2 proceeds to step S906 if not driven. In step S902, the correction coefficient α is set according to the focal length of the taking lens 1 and the moving direction of the subject with reference to the table shown in FIG. In step S903, the correction drive amount Cn is calculated by the following equation. Cn = α × Sn × TEN (4) This correction drive amount Cn is the amount by which the image plane of the subject moves during the time TEN. At the next focus detection, the correction drive amount Cn that makes the defocus amount zero is calculated. The correction coefficient α is a coefficient for correcting even a subject that moves toward the camera at a constant speed, because it does not become a constant speed when converted into the image plane movement amount. The correction coefficient α is generally larger than 1 when the subject approaches, and smaller than 1 when the subject moves away. Since the correction coefficient α depends on the focal length of the taking lens 1, it may be changed according to the lens information.

In step S904, the lens drive amount DR in which the correction drive amount Cn is added by the movement of the subject is calculated by the following equation. DR = DFn + Cn (5) In step S906, since the previous drive was not performed, the correction drive amount Cn is set to 0. When the above process is completed, the process returns to the focus determination subroutine of FIG.

In step S807 after returning, tracking display is performed on the display unit 14, and the process returns to the main program of FIG. On the other hand, in step S808, it is determined whether or not the previous focus was obtained, and if the focus is obtained, step S810 is performed.
If not, the process proceeds to step S809.
In steps S809 and S810, it is determined whether the defocus amount DFn is within the focusing range. ZO
NEN and ZONEW are predetermined values indicating an allowable range in focus determination, and ZONEN <ZONEW. Here, the focus zone width may be variable depending on the focal length of the taking lens 1 and the diaphragm. If the current defocus amount is within the in-focus range, the process proceeds to step S811, and if it is out of the in-focus range, the process proceeds to step S812. In step S811,
The focus flag is set, and in step S813, focus display is performed on the display unit 14. In step S812, the focus flag is cleared.

In step S814, the focus adjustment mode MO
It is determined whether the DE is in the one-shot mode (S). If the DE is in the one-shot mode, the process proceeds to step S815, and if not, the process proceeds to step S817. Step S815
Then, the release permission flag is set, the focus lock flag is set, and the release switch SW2 interrupt is permitted. Then, in step S816, focus lock display is performed. In step S817, the lens drive amount D
After setting R to 0, the process returns to the main program of FIG. In step S818, it is determined whether or not the focus is locked, and if the focus is locked, it is determined that the framing after focusing is changed, and step S816 is performed.
Otherwise, to step S819. In step S819, it is determined whether or not it is the front pin, and if it is the front pin, the process proceeds to step S820, and if it is the rear pin, the step S820.
Proceed to 821. In step S820, the front pin display is performed on the display unit 14, while in step S821, the rear pin display is performed. In step S822, the lens drive amount DR is set to DF.
After setting n, return to the main program in FIG.

Now, the low contrast processing of the focus determination subroutine of FIG. 8 will be described with reference to the flowchart shown in FIG. In step S1001, it is determined whether the focus is locked or not. If the focus is locked, the focus lock is displayed in step S816 in FIG.
Otherwise, to step S1002. In step S1002, it is determined whether or not the previous low contrast was detected. If the previous low contrast was detected, the process proceeds to step S1005, and if not, the process proceeds to step S1003. In step S1003, it is determined whether or not the object is a moving object. If the object is a moving object, the process proceeds to step S804 in FIG. 8; otherwise, the process proceeds to step S1004. In step S1004, 0 is set to the lens drive amount pulse DP. That is, if the still subject has previously become a low contrast this time, the lens drive is not performed once. In step S1005, the focus flag is cleared, and in the following step S1006, low contrast is displayed, and then the process returns to the main program in FIG.

Returning again to the main program of FIG.
In step S409, the lens driving subroutine shown in FIG. 11 is executed. The lens driving process will be described with reference to the flowchart of FIG. In step S1101, it is determined whether the focus is locked. If the focus is locked, the process proceeds to step S1123, and if not, the process proceeds to step S1102. In step S1102, it is determined whether or not the focus is achieved, and if the focus is achieved, the step S110 is performed.
If not, the process proceeds to step S1103. In step S1103, it is determined whether or not focus detection is impossible. If not possible, the process proceeds to step S1116, and if not, the process proceeds to step S1104. Step S110
In step 4, it is determined whether or not the driving direction of the photographing lens 1 is reversed from the previous time. If it is reversed, the process proceeds to step S1105, and if not, the process proceeds to step S1106.
In step S1105, an inversion flag indicating inversion of the lens driving direction is set, while in step S1106, the inversion flag is cleared.

In step S1107, since the driving direction of the photographing lens 1 is reversed by the subsequent lens driving, the lens driving amount DR in which the backlash is corrected is calculated. In step S1108, the previous lens drive amount pulse DP is stored in the variable PDP, and the current defocus amount DFn is DFn-1.
To store. Next, in step S1109, the lens drive amount pulse DP is calculated from the lens drive amount DR by the following equation. DP = KL × KB × DR (6) Here, KL and KB are coefficients shown in the equation (2). In step S1110, the lens drive amount pulse DP is set in the pulse count register DPR, and the pulse counter ECNT that counts the pulses from the encoder 13 is cleared.

At step S1111, whether DP is positive or not is determined.
In other words, determine whether the lens drive direction is infinite,
If it is an infinite direction, the process proceeds to step S1112, and if it is the closest direction, the process proceeds to step S1113. Step S111
In 2, start driving the AF motor 10 toward infinity,
On the other hand, in step S1113, driving of the AF motor 10 in the close-up direction is started. In step S1114, a driving flag indicating that the lens is currently being driven is set,
In a succeeding step S1115, the pulse counter interrupt is permitted and the process returns to the main program of FIG. The pulse counter interrupt occurs when DPR = ECNT, and the pulse counter interrupt routine shown in FIG. 12 is executed.

In step S1116, it is determined whether or not it was the previous low-con, and if it was the previous low-con, the process proceeds to step S1117 to perform scanning, and if not, the process proceeds to step S1104. In step S1117,
It is determined whether or not scanning is prohibited. If prohibited, the process proceeds to step S1122, and if not prohibited, the process proceeds to step S1118. In step S1118, it is determined whether or not scanning is currently being performed. If scanning is in progress, the process proceeds to step S1121, and if not, the process proceeds to step S1119. In step S1119, a driving flag indicating that driving is in progress and a scanning flag indicating that scanning is in progress are set, and in subsequent step S1120, scanning of the taking lens 1 is started. In step S1121, the pulse counter interrupt during scanning is prohibited. Step S112
In 2, the scan is prohibited, so the scan flag is cleared, and in the next step S1123, the AF motor 10
To stop. In step S1123, since the taking lens 1 is not driven, the driving flag indicating that the lens is being driven is cleared, and the process returns to the main program in FIG.

Next, the pulse counter interrupt processing will be described with reference to the flowchart of FIG. When a pulse counter interrupt occurs, first in step S1201, the AF
The motor 10 is stopped, and the pulse counter interrupt is prohibited in the following step S1202. Step S1203
Since the photographing lens 1 is stopped, the driving flag is cleared, and in step S1204, the previous driving flag indicating that the lens has been driven last time is set. When the above process is completed, the process returns to the program when the interrupt occurred.

When the lens driving subroutine shown in FIG. 11 is completed, the process returns to the main program of FIG. 4 and returns to step S402 to repeat the above-mentioned processing again.
Here, when the release switch SW1 is on and the release switch SW2 is off, that is, when the shutter release button is half pressed, the above flow of FIG. 4 is repeated. However, when the focusing mode is focused in the continuous mode (C) or the one-shot mode (S), the shutter release is permitted, and the SW2 interrupt is generated when the release switch SW2 is turned on.

According to the flowchart shown in FIG. 13, SW
2 Interrupt processing will be described. In step S1301, a mirror up flag indicating mirror up is set, and SW
2 Disable interrupts and start mirror up operation. In step S1302, it is determined whether or not the subject is moving. If the subject is stationary, the process proceeds to step S1310, and if the subject is moving, the process proceeds to step S1303. Step S130
From 3 onward, the taking lens 1 is driven while the mirror is raised to take a focused image, so the lens drive amount for correcting the focus shift due to the release time lag is calculated. In step S1303, a tracking calculation 2 subroutine for predicting the lens position at the end of the mirror-up is executed.

In step S1401 of FIG. 14, it is determined whether or not the previous drive is performed, and if the previous drive is performed, step S1 is performed.
Proceeding to 402, the table of α shown in FIG. 17 is referred to.
In step S1403, the correction drive amount Cn is calculated by the following equation. Cn = α × Sn × (AFT1-ITn + TR-INTT / 2) (7) where TR is the release time lag and INTT is the CCD
Charge accumulation time, ITn is CCD accumulation start time, AF
T1 is the current time of the free running timer.
In step S1404, Cn is set to 0 when the taking lens 1 has not been driven last time. Step S1405
Then, it is determined whether or not the taking lens 1 is currently being driven,
If the lens is being driven, the process proceeds to step S1407, and if the lens is not being driven, the process proceeds to step S1406. In step S1406, Cn is set in the correction drive amount CDR. In step S1407, the correction drive amount CDR is calculated by the following equation. CDR = DFn + Cn (8) Then, the process returns to the SW2 interrupt routine of FIG.

15 and 16 are diagrams showing the loci of the object image plane position and the lens position by the taking lens 1, in which the vertical axis represents the position Z and the horizontal axis represents the time t. FIG. 15 shows the loci of the two when the release is performed while the lens is not being driven. In this case, since the latest focus detection result by CCD accumulation has not been obtained, the defocus amount at the end of the previous lens drive is unknown. However, since the lens is driven so that the defocus amount becomes 0 at the next charge accumulation at the time of half-pressing, the defocus amount at the CCD accumulation at the previous lens drive should be 0. Meanwhile, FIG.
Shows the loci of both when the lens is released during driving. In this case, since the latest focus detection result is obtained, the correction drive amount CDR is calculated by the above equation (8).

After returning from the tracking calculation 2 subroutine shown in FIG. 14, it is determined in step S1304 in FIG. 13 whether or not the lens is currently being driven.
The process proceeds to 1306, and if driving is not in progress, step S1305
Go to. In step S1305, the lens drive amount DR is set to (DR + CDR), and the drive pulse DP is set to (KL ×
KB × CDR). On the other hand, in step S1306, the correction drive amount CDR is set to the lens drive amount DR, and the drive pulse DP is set to (KL × KB × CDR−ECNT). In step S1307, the pulse counter interrupt is prohibited and then DP is set in the pulse count register DPR to enable the pulse counter interrupt. Step S
In 1308, it is determined whether or not the lens is currently being driven. If the lens is being driven, the process proceeds to step S1310, and if not, the process proceeds to step S1309. In step S1309, lens driving is started and the driving flag is set.

In step S1310, the process waits until the mirror-up is completed, and when the mirror-up is completed, step S13.
The process proceeds to 1311 and waits for the lens driving to end. When the lens driving is completed, the process advances to step S1212 to control the shutter control circuit 16 to perform exposure. In step S1313 after the end of exposure, the mirror down is started, and a predetermined time is waited until the mirror bound disappears and becomes stable. After a lapse of a predetermined time, in step S1314, it is determined whether or not the subject is a moving body, and if it is a moving body, the switch SW2 interrupt is prohibited in order to guarantee the focus detection between the frames.
To step S503, and if stationary, step S503
In step 1315, the switch SW2 interrupt is permitted.

In the SW2 interrupt subroutine, if the lens is being driven at the end of the mirror up, the shutter curtain is started after the drive of the photographing lens 1 is completed. If the lens drive remaining amount is compared with a predetermined value and is equal to or less than a predetermined value, the shutter curtain may start traveling.

In this way, the predicted defocus amount for the moving object that was being tracked before exposure at the time of the first focus detection after exposure is calculated, and a plurality of defocuses detected in a plurality of focus detection areas at the same point are calculated. Since the shooting lens after exposure is driven to be driven based on the defocus amount that is closest to the predicted defocus amount in the amount, it is possible to accurately capture the moving subject that was being tracked before exposure, even after exposure. Subsequently, the photographing lens can be driven to track the moving subject.

In the configuration of the above embodiment, the AF module 7 and the CPU 8 are the focus detecting means, and the CPU 8 is the stationary movement determining means, the image plane moving speed calculating means, the predicted defocus amount calculating means, the tracking drive amount calculating means and the correction. The AF motor 10, the driving mechanism 11, and the coupling 12 constitute driving means.

[0044]

As described above, according to the present invention, a predicted defocus amount for a moving object tracked before exposure at the time of first focus detection after exposure is calculated, and a plurality of focus detections are performed at the same point. Of a plurality of defocus amounts detected in the area, the defocus amount that is the closest to the predicted defocus amount and the image plane moving speed of the moving subject that was detected before exposure are used to shoot for the moving subject. Since the tracking drive amount for tracking the lens without delay is calculated, it is possible to accurately capture the moving subject that was being tracked before the exposure even after the exposure, and then continue to drive the shooting lens for the moving subject. can do.

[Brief description of drawings]

FIG. 1 is a diagram for responding to a complaint.

FIG. 2 is a block diagram showing the configuration of an embodiment.

FIG. 3 is a diagram showing a locus of image plane positions of a moving main subject and a background subject and a locus of positions of photographing lenses.

FIG. 4 is a flowchart showing a main program for focus adjustment control.

FIG. 5 is a flowchart showing a CCD accumulation control subroutine.

FIG. 6 is a flowchart showing a defocus amount calculation subroutine.

FIG. 7 is a flowchart showing a moving body determination subroutine.

FIG. 8 is a flowchart showing a focus determination subroutine.

FIG. 9 is a flowchart showing a tracking calculation 1 subroutine.

FIG. 10 is a flowchart showing a low contrast process at the time of focusing determination.

FIG. 11 is a flowchart showing a lens driving subroutine.

FIG. 12 is a flowchart showing a pulse counter interrupt routine.

FIG. 13 is a flowchart showing a SW2 interrupt routine.

FIG. 14 is a flowchart showing a tracking calculation 2 subroutine.

FIG. 15 is a diagram showing a locus between a subject image plane position and a lens position in the case of release when the lens is not being driven.

FIG. 16 is a diagram showing a locus between a subject image plane position and a lens position when a release is performed during driving of a lens.

FIG. 17 is a diagram showing a relationship between a focal length of a photographing lens and a moving direction of a subject and a correction coefficient α.

[Explanation of symbols]

 1 Shooting Lens 2 Subject 3 Main Mirror 4 Penta Prism 5 Eyepiece 6 Sub Mirror 7 AF Module 8 CPU 9 Lens Information Memory 10 AF Motor 11 Drive Mechanism 12 Coupling 13 Encoder 14 Display 15 Mirror Control Circuit 16 Shutter Control Circuit 100 Focus Detection Means 101 Stationary movement determination means 102 Image plane movement speed calculation means 103 Tracking drive amount calculation means 104 Correction means 105 Driving means 106 Predicted defocus amount calculation means

Claims (1)

[Claims] 1. A plurality of focus detection areas are provided in a photographing screen,
A focus detection unit that repeatedly detects a defocus amount indicating the focus adjustment state of the photographing lens for each focus detection region, and at least based on the current and past defocus amounts detected by the focus detection unit, or Stationary movement determination means for determining movement, and image plane movement for calculating a movement speed of a subject image plane imaged by the photographing lens based on at least current and past defocus amounts detected by the focus detection means. When the movement of the subject is determined by the speed calculation means and the stationary movement determination means, the minimum defocus amount among the plurality of defocus amounts detected by the focus detection means and the image plane movement speed calculation Tracking drive for tracking the photographing lens with respect to the moving subject without delay based on the image plane moving speed calculated by the means. And a correction for correcting the tracking drive amount calculated by the tracking drive amount calculation unit so that the photographing lens focuses on the moving subject at the time of exposure when the shutter is released. Means for driving the photographing lens according to the tracking drive amount calculated by the tracking drive amount calculation unit or the tracking drive amount corrected by the correction unit, the image plane Predictive defocus amount calculation means for calculating a predicted defocus amount of the photographing lens for the moving object at the time of first focus detection after exposure, based on the image plane moving speed of the moving object calculated by the moving speed calculation means. The tracking drive amount calculation means includes a plurality of defocus amounts detected by the focus detection means only at the time of first focus detection after exposure. , The moving defocus amount that is closest to the predicted defocus amount calculated by the predicted defocus amount calculation unit and the image plane moving speed calculated by the image surface moving speed calculating unit On the other hand, a focus adjustment device for calculating a tracking drive amount for tracking the photographing lens without delay.