JP3213995B2 - Focus adjustment device - Google Patents

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 driving a photographing lens on a moving subject.

[0002]

2. Description of the Related Art From among a plurality of focus detection areas set in a photographing screen, a focus detection area closest to the current focal point of a photographing lens, that is, a focus detection area having a minimum defocus amount is selected. Based on the defocus amount detected in the detection area, a tracking drive amount for tracking the shooting lens with no delay with respect to the moving subject is calculated, the shooting lens is driven, and when the shutter is released, shooting is performed at the time of exposure. 2. Description of the Related Art There is known a focus adjustment device that corrects a tracking drive amount and drives a photographing lens so that a lens is focused on a moving subject.

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

[0004]

However, in the conventional focus adjusting device, as shown in FIG. 3, for example, when there is a background subject moving at substantially the same speed as the main subject, focus detection after exposure ( At the time of I), the focus detection area closest to the current focal point of the photographing 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 area. At the time of the first focus detection after the exposure, the focus adjustment of the photographing lens is performed on the background subject having a smaller defocus amount than the main subject, and there is a problem that the background subject is tracked thereafter.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a focus adjusting device that accurately captures a moving subject that has been tracked before exposure even after exposure, and drives the shooting lens to track.

[0006]

Means for Solving the Problems The present invention will be described with reference to FIG. 1 which is a claim correspondence diagram. The present invention has a plurality of focus detection areas in a shooting screen, and captures images for each focus detection area. Focus detecting means 100 for repeatedly detecting a defocus amount indicating a focus adjustment state of a lens; and focus detecting means 1
00, every time focus detection is performed, movement of the subject image plane formed by the photographing lens based on the current and past defocus amounts selected from the plurality of defocus amounts in the plurality of focus detection areas. Speed (image plane moving speed)
Is calculated based on the image plane moving speed at the time of the previous focus detection calculated by the image plane moving speed calculating means 101. The defocus amount estimating means 102 for estimating and the defocus amount closest to the defocus amount estimated by the defocus amount estimating means 102 from the plurality of defocus amounts detected in the plurality of focus detection areas during the current focus detection. A defocus amount selecting unit 103 for selecting a focus amount; a defocus amount selected by the defocus amount selecting unit 103; and an image plane moving speed at the time of the current focus detection calculated by the image plane moving speed calculating unit 101. On the basis of the,
Tracking drive amount calculating means 104 for calculating a tracking drive amount for causing the photographing lens to track the moving subject without delay
And a lens drive control unit 105 that drives and controls the photographing lens according to the tracking drive amount calculated by the tracking drive amount calculation unit 104.

[0007]

Based on the image plane moving speed of the moving subject calculated at the time of the previous focus detection, the defocus amount of the moving subject at the time of the current focus detection is estimated, and detected at a plurality of focus detection areas at the time of the current focus detection. The defocus amount closest to the defocus amount estimated value is selected from the plurality of defocus amounts thus obtained. Then, a tracking drive amount for tracking the moving subject is calculated based on the selected defocus amount and the image plane moving speed calculated at the time of the current focus detection, and the photographing lens is driven and controlled according to the tracking drive amount. As a result, a moving subject tracked before the exposure can be accurately captured even after the exposure.

[0008]

FIG. 2 shows the structure of a camera according to one embodiment. A part of the light beam 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 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
Comprises a well-known focus detection optical system, performs photoelectric conversion by a signal from the CPU 8, and further outputs the photoelectric conversion output to a CP.
Transfer to U8. The CPU 8 performs a focus adjustment control by executing a control program described later. Lens information memory 9
Transfers lens information such as the focal length of the photographing lens 1 and a conversion coefficient between the defocus amount and the lens drive amount to the CPU 8 according to a signal from the CPU 8.

The AF motor 10 is activated by a signal from the CPU 8 and drives the driving mechanism 11 of the photographing lens 1 via the coupling 12. Further, the encoder 13
An encoder pulse corresponding to the rotation 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 the up / down of the main mirror 3 by a signal from the CPU 8, and 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 is lowered by the mirror control circuit 15. The release switch SW1 is
The switch is turned on when the shutter release button is half-pressed, and the release switch SW2 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. When a main switch (not shown) is turned on, the CPU 8 starts executing the main program. 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 a one-shot mode (hereinafter, also referred to as an S mode). The one-shot mode is a focus adjustment mode in which the photographing lens 1 is driven when the shutter release button is half-pressed, and the lens driving is stopped once the subject is focused. Next, in step S402, it is determined whether or not the shutter release button is half-pressed by the release switch SW1. If the shutter release button is half-pressed, the process proceeds to step S403; otherwise, the process returns to step S401. Step S403
Then, the subroutine of the CCD accumulation control shown in FIG. 5 is executed.

The CCD accumulation control will be described with reference to the flowchart of FIG. In step S501, it is determined whether or not the photographing lens 1 is currently being driven. If the lens is being driven, the process proceeds to step S502; if not, step S50 is performed.
Proceed to 3. In step S502, it is determined whether or not the scanning is being performed. If the scanning is being performed, the process proceeds to step S503. If not, the process returns to step S501 and waits until the lens driving is completed. After the lens driving is completed, 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 for the variable ITn. Further, variables TEn and TEn-1 representing time intervals of focus detection are calculated and stored. In step S504, after the release
It is determined whether or not it is the first focus detection, and if it is the first focus detection, the process proceeds to step S506; otherwise, the process proceeds to step S505. In step S505, the previous focus detection interval TEn is stored in a variable TEN representing a standard time for performing the predictive driving. This variable TEN is used as a time parameter for predictive driving when a release is not performed.

In step S506, the lens position ECNT at the start of accumulation is substituted for a variable PLC1. In the following 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 scanning is currently being performed. If a scan is being performed, the process proceeds to step S510; otherwise, the process returns to the main program in FIG. In step S510, the lens position ECNT at the end of the accumulation is substituted for the variable PLC2, and in the following step S511, the variables PLC1, PL
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 about the lens is obtained from the lens information memory 9. Then, in step S406, a defocus calculation subroutine shown in FIG. 6 is executed.

The operation of calculating the defocus amount will be described with reference to the flowchart of FIG. In step S601, based on the CCD output data stored in the memory, the defocus amounts DFa, DFa,
DFb and DFc are calculated. In step S602, it is determined whether or not focus detection is impossible in all areas.
If the focus can be detected in one area, the process proceeds to step S603. In step S603, it is determined whether it is the first time after the shutter release button is half-pressed, and if it is the first time, the process proceeds to step S618; otherwise, the process proceeds to step S60.
Proceed to 4. In step S604, it is determined whether or not the object is a front rotating body. If the object is a moving object, the process proceeds to step S605; otherwise, the process proceeds to step S615. Step S60
In step 5, it is determined whether or not the first focus detection after the shutter release is performed. If the focus detection is the first time, the process proceeds to step S606 to calculate a predicted defocus amount at the time of distance measurement, and otherwise proceeds to step S617.

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

In step S609, it is determined whether or not the focus cannot be detected at this time. If the focus cannot be detected, the process returns to the main program of FIG.
Proceed to. In step S610, a counter COUNT for determining whether or not the number of focus detections required for the prediction calculation is reached.
Is incremented. In step S611, it is determined whether or not the scan is currently being performed because the focus cannot be detected. If the scan is being performed, the process proceeds to step S612; otherwise, the process returns to the main program in FIG. In step S612, since the focus can be detected at 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, since the charge accumulation and the focus detection calculation are performed while driving the photographing lens 1, the defocus amount obtained by correcting the lens driving amount during the accumulation calculation 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 drive amount. The number, ECNT, is a pulse count indicating the current relative lens position. Here, the lens position at the center of the charge accumulation is set as the midpoint between the lens positions at the start and end of the accumulation.

In step S615, it is determined whether or not the camera is in focus. If the camera is in focus, the process proceeds to step S617 so that the current priority is given. If the camera is not in focus, the closest priority is given to step S616. Proceed to. In step S616, an area indicating the closest defocus amount is selected,
Store in DFn. In step S617, 0 is stored in the estimated defocus amount DFes during distance measurement. Step S6
At 18, the COUNT is initialized to 0 since the focus is detected for the first time after the shutter release button is half-pressed. Step S
In step 619, the low-con flag is set because detection is not possible in all areas.

Next, returning to the main program of FIG. 4, in step S407, the moving object determination subroutine shown in FIG. 7 is executed. Here, the moving object determination processing will be described with reference to the flowchart shown in FIG. In the moving object determination subroutine, it is determined whether the subject is a moving object or stationary. In step S701, it is determined whether or not a scan is being performed. If the scan is being performed, the process proceeds to step S717; otherwise, the process proceeds to step S702. This is because moving body determination is not performed immediately after scanning. Step S702
It is determined whether or not focus detection is impossible. If detection is not possible, the process proceeds to step S714; otherwise, the process proceeds to step S7.
Go to 03. In step S703, it is determined whether or not the driving direction has been reversed by the previous lens driving. If the driving direction has been reversed, the process proceeds to step S717; otherwise, the process proceeds to step S704. This is because the driving mechanism 11 at the time of inversion driving is used.
This is to avoid erroneous determination of stationary / moving due to backlash of the above.

In step S704, the previous image plane movement amount P
n is stored in Pn−1, and in the subsequent step S705,
It is determined whether T is greater than one. If it is larger than 1, the process proceeds to step S706; otherwise, the process proceeds to 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 a lens driving amount during focus detection. In step S707, it is determined whether or not Pn and Pn-1 are different codes. If Pn and Pn-1 are different codes, the process proceeds to step S718; otherwise, the process proceeds to step S708. This determination is for avoiding accidentally entering the tracking mode due to camera shake or the like.

In step S708, it is determined whether or not the body is a front rotating body. If the body is a front rotating body, the process proceeds to step S710. If the body is stationary, the process proceeds to step S709. This is to prevent the hunting of the moving object determination and to immediately exit the tracking mode once the moving object is determined. 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 larger, the process proceeds to step S711, and if smaller, the process proceeds to step S718. . In step S710, it is determined whether 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.
Proceed to.

In step S711, the previous image plane movement amount P
The ratio between n-1 and the current image plane movement amount Pn is calculated. If the ratio is within a predetermined range, the subject is determined to be a moving object, and the process proceeds to step S712. If the ratio is outside the predetermined range, step S71 is performed.
Proceed to 8. This is to prevent the subject from changing when the composition of the camera is changed, and to prevent the change in the subject from being erroneously determined as the movement of the subject. Note that 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 the moving object is determined by the above-described determination. In the following step S713, the image plane moving speed Sn is calculated from the image plane moving amount Pn and the time interval TEn, and the main program shown in FIG. Return to

In step S714, it is determined whether or not it was the last low-con.
Go to step S17, otherwise go to step S715.
This is to prevent the moving object from being determined when the low contrast has been performed twice consecutively. In step S715, it is determined whether or not the body is a front rotating body. If the body is a front rotating body, the process proceeds to step S716; otherwise, the process proceeds to step S717.
Proceed to. This is because if it is a front rotating body, it is highly likely that it is also a moving body this time, but there is a possibility that the subject has missed from the distance measurement area due to the movement of the subject, so do not perform the normal low contrast operation That's why. Step S7
At 16, the image plane movement amount is indefinite because it is a low contrast, 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 undefined. In step S718, the moving object flag is cleared because the subject is determined to be a still subject.

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

In step S805, a release permission flag is set to permit release, the focus lock flag is cleared, the focusing flag is cleared, and the release switch SW2 interrupt is permitted. Subsequent step S8
At 06, a subroutine of tracking calculation 1 shown in FIG. 9 is executed to perform predictive driving.

In step S901 of FIG. 9, it is determined whether or not the lens has been driven last time.
The process proceeds to step S906, and if not, the process proceeds to step S906. In step S902, the correction coefficient α is set based on the focal length of the photographing lens 1 and the moving direction of the subject with reference to the table shown in FIG. In step S903, the correction driving amount Cn is calculated by the following equation. Cn = α × Sn × TEN (4) The correction drive amount Cn is an amount by which the image plane of the subject moves during the time TEN. At the next focus detection, a correction drive amount Cn is calculated so that the defocus amount becomes zero. The correction coefficient α is a coefficient for correcting even an object moving at a constant speed toward the camera, since it does not become a constant speed when converted into an 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 taking into account the correction drive amount Cn due to the movement of the subject is calculated by the following equation. DR = DFn + Cn (5) In step S906, since the previous driving was not performed, the correction driving amount Cn is set to 0. Upon completion of the above processing, the process returns to the focusing determination subroutine of FIG.

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

In step S814, the focus adjustment mode MO
It is determined whether or not the DE is in the one-shot mode (S). If the DE is the one-shot mode, the process proceeds to step S815; otherwise, 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 driving 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. If the focus is locked, it is determined that framing is to be changed after focusing, and step S816 is performed.
Otherwise, to step S819. In step S819, it is determined whether or not it is the front focus. If it is the front focus, the process proceeds to step S820.
Proceed to 821. In step S820, the front focus is displayed on the display 14, while in step S821, the back focus is displayed. In step S822, DF is added to the lens drive amount DR.
After setting n, the process returns to the main program of FIG.

Here, 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 or not the focus is locked. If the focus is locked, step S816 in FIG. 8 is performed to display the focus lock.
The process proceeds to step S1002 otherwise. In step S1002, it is determined whether or not it was the previous low contrast, and if it is the previous low contrast, the process proceeds to step S1005. If not, the process proceeds to step S1003. In step S1003, it is determined whether 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, when the low-contrast image is obtained this time for the still subject, the lens drive is not performed once. In step S1005, the in-focus flag is cleared, and in step S1006, after displaying the low contrast, the process returns to the main program of FIG.

Returning again to the main program of FIG.
In step S409, a 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 or not the focus is locked. If the focus is locked, the process proceeds to step S1123. If not, the process proceeds to step S1102. In step S1102, it is determined whether or not the subject is in focus.
Proceed to 1123, otherwise proceed to step S1103. In step S1103, it is determined whether or not focus detection is impossible. If not, the process proceeds to step S1116; otherwise, 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 has been reversed from the last time. If the driving direction has been reversed, the process proceeds to step S1105. If not, the process proceeds to step S1106.
In step S1105, an inversion flag indicating the 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 has been corrected is calculated. In step S1108, the previous lens driving amount pulse DP is stored in the variable PDP, and the current defocus amount DFn is set to DFn-1.
To be stored. Next, in step S1109, a lens driving amount pulse DP is calculated from the lens driving amount DR by the following equation. DP = KL × KB × DR (6) Here, KL and KB are coefficients shown in equation (2). In step S1110, the lens drive amount pulse DP is set in the pulse count register DPR, and the pulse counter ECNT for counting pulses from the encoder 13 is cleared.

In step S1111, whether DP is positive or not is determined.
That is, it is determined whether or not the driving direction of the lens is infinite,
If the direction is infinite, the process proceeds to step S1112, and if the direction is close, the process proceeds to step S1113. Step S111
In 2, the AF motor 10 starts to be driven toward infinity,
On the other hand, in step S1113, the driving of the AF motor 10 is started in the close direction. 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. Note that the pulse counter interrupt occurs when DPR = ECNT, and executes the pulse counter interrupt routine shown in FIG.

In step S1116, it is determined whether or not it was the previous low contrast. If it was the last low contrast, the flow proceeds to step S1117 to perform scanning, and if not, the flow proceeds to step S1104. In step S1117,
It is determined whether or not scanning is prohibited. If it is prohibited, the process proceeds to step S1122, and if not, the process proceeds to step S1118. In step S1118, it is determined whether or not a scan is being performed. If the scan is being performed, the process proceeds to step S1121, and if the scan is not being performed, 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 step S1120, scanning of the photographic lens 1 is started. In step S1121, a pulse counter interrupt during scanning is prohibited. Step S112
In step 2, since the scan is prohibited, the scan flag is cleared, and in step S1123, the AF motor 10
To stop. In step S1123, since the photographing 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 of 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, AF
The motor 10 is stopped, and in a succeeding step S1202, the pulse counter interrupt is prohibited. Step S1203
Then, since the photographing lens 1 is stopped, the driving flag is cleared, and in step S1204, a previous driving flag indicating that the driving was performed last time is set. When the above processing is completed, the program returns to the program at the time of occurrence of the interrupt.

When the lens driving subroutine shown in FIG. 11 is completed, the process returns to the main program of FIG. 4, returns to step S402, and repeats the above-described processing.
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 focus is adjusted in the continuous mode (C) or the one-shot mode (S), the shutter release is permitted, and when the release switch SW2 is turned on, an SW2 interrupt is generated.

According to the flowchart shown in FIG.
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 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
In the third and subsequent steps, the lens driving amount for correcting the focus shift due to the release time lag is calculated in order to drive the photographing lens 1 during the mirror up and to take a focused photograph. In step S1303, a subroutine of tracking calculation 2 for estimating the lens position at the end of mirror up is executed.

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

FIGS. 15 and 16 are diagrams showing the trajectory between the object image plane position and the lens position by the photographic lens 1. The vertical axis represents the position Z, and the horizontal axis represents the time t. FIG. 15 shows both trajectories when the lens is released when the lens is not being driven. In this case, since the focus detection result based on the latest CCD accumulation is not obtained, the defocus amount at the end of the previous lens driving is unknown. However, when the lens is half-pressed, the lens is driven so that the defocus amount becomes 0 at the next charge accumulation, and the defocus amount should have been 0 at the time of CCD accumulation by the previous lens drive. On the other hand, FIG.
Shows the trajectories of both lenses when the lens is released during driving of the lens. In this case, since the latest focus detection result is obtained, the correction driving amount CDR is calculated by the above equation (8).

After returning from the tracking operation 2 subroutine shown in FIG. 14, it is determined in step S1304 in FIG. 13 whether or not the lens is currently being driven.
Proceed to 1306, and if not driving, step S1305
Proceed to. In step S1305, the lens drive amount DR is set to (DR + CDR), and the drive pulse DP is set to (KL × CDR).
(KB × CDR) is set. 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 disabled, DP is set in the pulse count register DPR, and the pulse counter interrupt is enabled. 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; otherwise, the process proceeds to step S1309. In step S1309, lens driving is started and a driving flag is set.

In step S1310, the process waits until the mirror-up is completed.
Proceed to 1311 and wait for lens drive to end. Upon completion of the lens driving, the flow advances to step S1212 to control the shutter control circuit 16 to perform exposure. In step S1313 after the end of the exposure, the mirror down is started, and a predetermined time is waited until the mirror bounce 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. If the moving body is a moving body, the switch SW2 interrupt is disabled to guarantee focus detection between frames while FIG.
The process proceeds to step S503 of step S503.
Proceed to 1315 to enable the switch SW2 interrupt.

In the subroutine of the SW2 interrupt, if the lens is being driven at the end of the mirror up, the shutter curtain starts running after the drive of the photographing lens 1 is completed. The running of the shutter curtain may be started if the remaining amount of the lens drive is equal to or smaller than a predetermined value.

As described above, the predicted defocus amount for the moving object tracked before the exposure at the time of the first focus detection after the exposure is calculated, and the plurality of defocus amounts detected in the plurality of focus detection areas at the same time are calculated. Since the tracking lens is driven after exposure based on the defocus amount closest to the predicted defocus amount in the amount, the moving subject that was tracked before exposure can be accurately captured 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 serve as focus detecting means, and the CPU 8 serves as image plane moving speed calculating means, defocus amount estimating means, defocus amount selecting means and tracking drive amount calculating means. CPU
8 and the AF motor 10 constitute lens drive control means, respectively.

[0044]

According to the present invention as described above, according to the present invention, prior to
To the image plane moving speed of the moving object calculated at the time of focus detection
Based on the current focus detection
The defocus amount is estimated, and multiple focuses are detected during the current focus detection.
From multiple defocus amounts detected in the point detection area
Select the defocus amount closest to the estimated defocus amount
I do. Then, select the defocus amount and the focus
The moving subject is determined based on the
Calculates the tracking drive amount for tracking and sets it as the tracking drive amount
Since the drive of the photographing lens is controlled in this way, the moving subject that was tracked before the exposure can be accurately captured even after the exposure, and the photographing lens can be continuously driven for the moving subject.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims.

FIG. 2 is a block diagram showing a configuration of one embodiment.

FIG. 3 is a diagram illustrating a locus of an image plane position of a moving main subject and a background subject, and a locus of a position of a photographing lens.

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

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

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

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

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

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

FIG. 10 is a flowchart showing low contrast processing at the time of focus 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 illustrating a locus between a subject image plane position and a lens position when the lens is released when the lens is not being driven.

FIG. 16 is a diagram illustrating a locus between a subject image plane position and a lens position when the lens is released during driving of the lens.

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

[Explanation of symbols]

 Reference Signs List 1 shooting lens 2 subject 3 main mirror 4 pentaprism 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

────────────────────────────────────────────────── ─── Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B ^7/ 28-7/38

Claims (1)

(57) [Claims] 1. A photographing screen having a plurality of focus detection areas,
Focus detection means for repeatedly detecting a defocus amount indicating the focus adjustment state of the taking lens for each focus detection area; and each time focus detection is performed by the focus detection means,
From among multiple defocus amounts of multiple focus detection areas
Image plane moving speed calculating means for calculating a moving speed of an object image plane formed by the photographing lens (hereinafter, referred to as an image plane moving speed) based on the selected current and past defocus amounts; Previous focus detection calculated by image plane moving speed calculation means
This time, based on the moving speed of the image plane,
Defocus to estimate the amount of defocus at the time of focus detection
An amount estimating means, which is detected in the plurality of focus detection areas during the current focus detection.
Out of a plurality of defocus amounts,
The default value closest to the defocus amount estimated by the estimation means
And the defocus amount selection means for selecting the carcass weight, the defocus selected in the defocus amount selection means
And the current focus calculated by the image plane moving speed calculating means.
The moving object based on the image plane moving speed at the time of point detection.
For tracking the taking lens without delay
A tracking drive amount calculating means for calculating a tail drive amount; and a tracking drive amount calculated by the tracking drive amount calculating means .
A lens driving control means for driving and controlling the photographing lens.
Focusing device, characterized in that it comprises a stage.