JPH0795138B2 - Automatic 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 an automatic focus adjustment device for a camera, and more particularly to an automatic focus adjustment device that can obtain appropriate focus adjustment even for a moving subject.

[0002]

2. Description of the Related Art In a camera equipped with an automatic focusing device, first, a defocus amount for a planned focal plane of a taking lens is calculated, and the lens is driven based on the calculation result to obtain a focused state. I am trying. Then, when the subject is a moving object and the defocus amount changes, the change speed of the defocus amount due to the movement of the subject is obtained, and the driving of the photographing lens is corrected by this to follow the moving subject. Then, a camera for focusing is already proposed.

The so-called focus determination for determining whether or not the photographic lens is at the in-focus position is usually performed while the photographic lens is stopped. That is, it is general that after the defocus amount is calculated, the photographing lens is driven, and the lens is stopped when the lens is driven by an amount corresponding to the calculated defocus amount, and the focus determination is performed at this point.

[0004]

However, in a camera which focuses on a moving subject as described above, the taking lens is always driven as the subject moves. Therefore, if the focus determination is performed after waiting for the photographing lens to stop, there is a problem that the focus determination cannot be performed forever because the subject is moving during that time. Further, conventionally, a so-called autofocus priority camera has been proposed in which a release operation is prohibited until a focused state is detected in order to reliably take a photograph in focus. In that case, you will not be able to take a picture forever, and you will miss the opportunity to shoot.

In order to solve this problem, it is conceivable to stop the lens at a predetermined timing for the focus determination, but this method has a problem that the taking lens is delayed in tracking the moving subject. Occurs.

Therefore, the present invention has been made to solve the above-mentioned problems, and automatic focus adjustment is performed so that an appropriate focus determination can be performed even in a camera that follows a moving subject and focuses on the subject. The purpose is to provide a device.

[0007]

SUMMARY OF THE INVENTION An automatic focus adjusting device according to the present invention comprises a focus detecting means for repeatedly calculating a defocus amount from a focus position of a photographing lens with respect to an object, and a plurality of repeatedly output from the focus detecting means. Based on the defocus amount of, the movement detection unit that detects the movement of the subject in the optical axis direction, and the defocus amount detected by the focus detection unit, the change amount of the defocus amount due to the movement of the subject. An arithmetic means for calculating the defocus amount taking into account, a driving means for driving the photographing lens, a first judging means for judging whether or not the photographing lens is being driven,
Second determining means for determining whether or not the subject is a moving body based on the detection result of the movement detecting means, third determining means for determining whether the photographing lens is at the in-focus position, and the first When the determination means determines that the taking lens is being driven, the second determination means determines whether or not the subject is a moving body. When it is determined that the subject is a moving body, the third determination means determines the focus. However, when it is determined that the subject is not a moving body, a control unit that does not perform the focus determination is provided.

[0008]

In the present invention, the focus determination is performed when the taking lens is being driven and the subject is a moving body, but not when the subject is not a moving body. That is, if the photographic lens is being driven at a certain point in time, if the subject is a moving object, there is a high possibility that the lens will continue to be driven after that point. Therefore, in this case, the focus determination is performed even while the lens is being driven. On the contrary, if the subject is not a moving body, the lens driven at that time is driven by a predetermined amount and then stopped. Therefore, in this case, focus determination is not performed at that time when the lens is being driven. Focus determination may be performed after the lens is stopped and the lens position is finalized. still,
This control is described in paragraph number [0063] in the examples.

[0009]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 shows a block configuration of the camera. The left side of the straight line AA ′ in the figure shows the interchangeable lens LZ, and the right side shows the body BD of the camera. Both can be mechanically connected by clutches 101 and 102, respectively.
2, when the interchangeable lens LZ is mounted on the camera body BD, the lens circuit 103 on the interchangeable lens LZ side and the reading circuit 104 on the camera body BD side are connected to the connection terminals JL1 to JL1.
It is designed to be electrically connected by JL5 and JB1 to JB5.

In this camera system, the interchangeable lens LZ
The object light that has passed through the lens system passes through the semi-transmissive portion in the center of the reflection mirror 105 of the camera body BD, and the sub-mirror 10
The optical system is configured so that the light is reflected by 6 and received by the CCD image sensor 107 in the focus detection module. The CCD image sensor 107 is used to measure the defocus amount of the interchangeable lens LZ, and a plurality of photoelectric conversion elements are arranged in an array so that signals from the photoelectric conversion elements are sequentially taken out. Can be used.

The interface circuit 108 drives the CCD image sensor 107, fetches subject data from the CCD image sensor 107, and sends the fetched data to the controller 109. The controller 109 is the CCD image sensor 10
Defocus amount | Δ | that indicates the amount of lens shift from the in-focus position based on the subject data from 7 and whether the lens position shifts to the front (front pin) or to the rear (rear pin). A signal with the defocus direction indicating the direction of deviation is calculated.

The motor MO1 is driven based on these signals, and its rotation is controlled by the slip mechanism 110 and the drive mechanism 11.
1 and the transmission mechanism 112 via the clutches 102, 101
Is transmitted to the optical system, the lens system of the interchangeable lens LZ is moved back and forth in the optical axis direction to perform focus adjustment. At this time, in order to monitor the amount of movement of the lens system, the camera body BD
The encoder 113 is connected to the drive mechanism 111 of (1), and the encoder 113 outputs a number of pulses corresponding to the drive amount of the lens system.

The slip mechanism 110 is an interchangeable lens LZ.
When a torque greater than a predetermined value is applied to the driven part of the motor M
The power of O1 slips and the motor M
No extra load is applied to O1.

Here, from the reading circuit 104 on the camera body side to the lens circuit 103 on the interchangeable lens side, a terminal JB1-
A power source through JL1, a clock pulse for synchronization during data transfer through terminals JB2-JL2, and a terminal JB.
A read start signal for starting the reading of data is sent via 3-JL3. In addition, serial data is sent from the lens circuit 103 to the reading circuit 104 via the terminals JL4-JB4. In addition, terminal JB51-JL
5 is a common ground terminal.

First, when the reading start signal is sent to the lens circuit 103, the data of the lens circuit 103 is sent to the reading circuit 104 in synchronization with the clock pulse. The reading circuit 104 converts the input serial data into parallel data KL based on the same clock pulse as the clock pulse output to the terminal and the lens circuit 103, and sends the parallel data KL to the controller 109. Based on the data K from the reading circuit 104, the controller 109 determines the defocus amount from the data of the subject image from the interface circuit 108.
| Δ | is calculated and the number of pulses N to be detected by the encoder 113 is N
Is calculated by calculating K · | Δ |. Further, the controller 109 rotates the motor MO1 in the clockwise direction or the counterclockwise direction through the motor driver 114 according to the signal in the defocus direction obtained from the data of the subject image, and the encoder 113 outputs a pulse equal to the calculated value N to the controller. When it is input to 109, it is determined that the lens system for focus adjustment has moved by the movement amount Δd to the focus position, and the rotation of the motor MO1 is stopped. When the focus is adjusted by such focus adjustment, a predetermined signal is sent from the controller 109 to the display circuit 115 to display the focus and the distance to the subject.

The general operation of the camera has been described above. Next, the control operation of the controller 109 will be described in more detail with reference to FIG. The same parts as those in FIG. 1 are designated by the same reference numerals.

Reference numeral 109 denotes a microcomputer (hereinafter referred to as a microcomputer) which operates in the controller described above.
Reference numeral 121 denotes an exposure control circuit that opens and closes the shutter according to the start and end of the exposure and controls the mirror up and diaphragm of the reflecting mirror 105 according to the mirror up signal. Reference numeral 122 denotes a photometric circuit, which digitizes a signal corresponding to the brightness of the subject and sends it to the microcomputer 109. A film sensitivity automatic reading circuit 123 reads the loaded film sensitivity, and the read film sensitivity is taken in by the microcomputer 109. 124 is the microcomputer 1
It is a one-frame winding circuit that drives a motor MO2 in accordance with a signal from 09 to wind one frame of film.
Is an exposure setting circuit for setting a shutter speed and an aperture value, and the set value is fetched by the microcomputer 109.

Reference numeral 107 denotes the CCD image sensor described above, and the image information of the object is obtained by the interface circuit 10.
It is taken in by the microcomputer 109 via 8. 114 is
A motor driver that controls the focus adjustment motor MO1 and an encoder 113 that outputs the drive amount of the motor MO1 as the number of pulses. Reference numerals 103 and 104 are a lens circuit and a reading circuit, and 115-1 and 115-2 are display circuits for displaying a focus detection state and a distance to a subject, respectively.

S ₁ is a switch which is turned on in the first step of pushing a release button (not shown).
_{When 1} is turned on, the microcomputer 109 is turned on, and the AF flow described later is executed. S ₂ is a switch which is turned on at the second stage of pressing the release button, and when the switch S ₂ is turned on, a release flow described later is executed. S ₃ is a switch that is turned on when the mirror up of the reflecting mirror is completed, and when a release member (not shown) is charged, the switch S ₃ is turned off. S ₄ is a shooting mode switch for switching between the continuous shooting mode and the single frame shooting mode, and S ₅ is a switch which is turned on when the exposure is completed and turned off when the film is wound up one frame. The primary side of each of the switches S _{1 to} S ₅ is grounded, and the secondary side connected to the microcomputer 109 is pulled up to the voltage V via the resistor R.

Next, the control operation of the camera having the above configuration will be described with reference to a flowchart. When the switch S ₁ is turned on in the first step of pressing the release, the microcomputer 109 executes the flowchart shown in FIG.

First, in step S1, various flags are reset, and in step S2, a free-run timer in the microcomputer 109 is started to know the time of each operation. Then, in step S3, through the reading circuit 104, the payout amount conversion coefficient K, which represents the focal length of the lens necessary for AF from the lens circuit 103, the open aperture value, and the amount of movement of the lens in the optical axis direction with respect to the rotation speed given to the lens,
The data of the open F value A _{00 of} the lens, the lens extension amount, and the data Dkl for converting the actual distance is the microcomputer 109.
Is taken into. In the next step S4, the set aperture value, shirt speed, etc. are read from the exposure setting circuit 125, and in the next step S5, a focus detection calculation as will be described later and an AF for driving the lens to the focus position based on the calculation result. The operation is performed. In step S6, the photometric result by the photometric circuit 122 is captured, and in step S7, the film sensitivity is captured by the film sensitivity reading circuit 123. In step S8, after the exposure calculation for exposure is performed by the above input data, the process returns to step S3 to perform the loop operation.

FIG. 4 shows the AF operation routine in step S5. First, step S401
Then, the subject light is integrated by the CCD image sensor 107 via the interface circuit 108. The data of the subject integrated by the CCD image sensor 107 in the next step S402 is taken out for each pixel (this operation is called a data dump), and the interface circuit 1
After being A / D converted in 08, it is taken in by the microcomputer 109. In step S403, a focus detection calculation is performed based on the subject data. A detailed description of the optical system to which the subject light is input and the focus detection calculation is omitted here since it is not necessary here, but details are described in JP-A-59-126517.

In the next step S404, preliminary calculation for follow-up correction is performed as described later. Step S
In 405, the defocus amount and its direction are calculated from the data from the CCD image sensor 107, and it is determined from the calculation result whether the defocus amount can be detected. If the subject image is greatly blurred or has low contrast, it is determined that detection is impossible and step S40 is performed.
Go to 6. In step S406, when focus detection is impossible, it is determined whether or not the operation of moving the lens to search for a focus detectable portion (hereinafter referred to as low contrast scan) is completed. When the low contrast scan is not executed, the low contrast scan is started in step S407. And this low contrast scan is repeated,
If focus detection is still impossible even after the low contrast scan is completed, a blinking display indicating that focus detection is impossible is displayed on the display circuit 115-1 in step S408, and thereafter step S6 in FIG. Return to.

On the other hand, if it is determined in step S405 that the defocus amount can be detected, step S4
In step 09, the lens drive amount ERR is calculated from the calculated defocus amount DF and the lens extension amount conversion coefficient K which is one of the lens data captured in step S3 of FIG.
(Pulse count unit) is calculated. ERR = DF × K

In step S410, it is determined whether the lens is stopped, and if it is stopped, step S41.
It is determined in 1 whether or not the lens is in focus, and if the lens is in the in-focus position, focus display is performed on the display circuit 115-1 in step S412, and then the process returns to the flow of FIG. , And proceeds to step S6. On the other hand, if the lens is out of focus, the process proceeds to step S413, and it is determined whether the defocus direction obtained in this routine execution is the opposite direction to the defocus direction obtained in the previous routine execution, and the defocus direction is determined. If the direction is reversed, the amount of backlash caused by the backlash of the lens drive system, which causes an error when the lens drive is reversed, is corrected, and step S424 is performed.
Proceed to. If the lens driving directions are the same, step S
In step 414, it is determined whether the AF drive mode for performing the follow-up correction is necessary, and if the follow-up correction mode is determined, the drive amount of the lens is corrected as the follow-up correction in step S415. In the next step S416, the focus determination for the tracking mode is performed. If the focus state is determined here, after the focus is displayed in step S417, the step S4 is performed.
Proceed to 24.

On the other hand, if the lens is being driven in step S410, the process proceeds to step S421, the defocus direction including the correction amount obtained in step S415 obtained this time is compared with the previous defocus direction, and the direction is determined. If it is determined that the lens has been inverted, the lens driving is stopped in step S423, and then the process returns. The reason why the lens is stopped here is to minimize the lens overshooting the in-focus position. If the defocus direction is not reversed, the process proceeds to step S422, and the step S4 is performed.
It is judged whether follow-up correction similar to 14 is necessary,
If the tracking correction is necessary, the process proceeds to step S415, but if not, the process proceeds to step S424.

In step S424, it is determined whether or not the lens is in the in-focus vicinity (near zone) based on the obtained defocus amount. If it is not in the near zone, step S425
In step S426, the lens is set to be driven at high speed, and in step S426, the lens is set to be driven at low speed. Then, after the lens is driven at the set drive speed in step S427, the process returns and the focus calculation is performed in step S6 and subsequent steps.

FIG. 5 is a more detailed description of steps S3 to S6 in FIG. 3 for explaining the follow-up correction. In step S501, the CCD image sensor 1
Time TM of the free-run timer at the start of integration of 07
1 is read, and in step S502, the count value T1 is read by the event counter EVTCNT for controlling the lens driving amount at the start of the integration. In step S503, integration of the CCD image sensor 107 is executed. CCD in step S504
The integration end time TM2 of the image sensor 107 is read from the free-run timer, and in step S505 the count value T2 is determined by the event counter EVTCNT at this time.
Is read. After that, steps S506 and S507
Then, as described above, the data dump of the CCD image sensor 107 and the focus detection calculation are performed. Of the time required to execute this routine, most of the above steps S
Spent for 501-S507. As will be described later, the value MI of the lens driving event counter EVTCNT at the integration center point obtained by executing the AF routine.
Is stored in the register R, and in step S508, the event count value MI stored in the register R is set to R ′ in the register storing the previous calculated value.
It is stored as L. In step S509, similarly, the time TMI at the integration center point is stored as TMIL in the register that stores the previous calculated value. In step S510, from the count values T1 and T2 of the event counter EVTCNT at the start of integration and at the end of integration obtained by the routine execution this time, the count value (T1 +
T2) / 2 is calculated and newly stored in the register R as MI. In step S511, similarly, the time (TM1 + TM2) / 2 at the center point of integration is calculated from the times TM1 and TM2 at the start and end of integration, and stored in the register.

In the next step, the lens drive amount between the previous integration center and the current integration center is calculated. This calculation will be described with reference to FIG.

The horizontal axis is time, and the vertical axis is the event counter E.
The value is VTCNT. T1 ₁ and T1 ₂ are the count values of the event counter EVTCNT at the start TM1 ₁ and TM1 ₂ of the integrations I ₁ and I ₂ , respectively, and T2 ₁ and T2 ₂ are the event counters of the integration end times TM2 ₁ and TM2 ₂ respectively. T3 ₁ and T3 ₂ are count values, respectively, which are count values of the event counter EVTCNT of the operation C ₁ and C ₂ end times TM3 ₁ and TM3 _{2 which} are performed after the same integration. or,
MIL and MI are the count values of the integration center point obtained from T1 ₁ and T2 ₁ , T1 ₂ and T2 ₂ , respectively. Where TM3
₁ = TM1 ₂ . The value of the event counter EVTCNT stored in the registers R and R'is adapted to be rewritten at the end of each operation, and the count value T3 ₂ of the event counter EVTCNT at the end time TM3 ₂ of the operation C ₂ is: The event count value MI is stored in the register R, and the event count value MIL obtained by the previous calculation C ₁ is stored in the register R ′. The event count value is a value obtained by converting the defocus amount obtained by calculation into the movement amount of the encoder, and indicates the position indicating the defocus amount from the subject image plane at each integration center point.

However, as shown in FIG. 18, the calculation C ₁
When the integration ends and the next integration I ₂ starts, the event count value becomes discontinuous. This is due to the characteristics of the CCD image sensor 107, integral T ₁ in TM3 ₁
This is because the event count value is rewritten according to the focus detection result of (3) and is caused by an error in the focus detection system. MIL-
The value of MI does not indicate an accurate lens movement amount in one integration cycle. Assuming that the gap of this discontinuous portion is DT, this value DT is a value SERR in which the calculation result is set in the encoder as the lens movement number at the end of the calculation C ₁ and an event counter indicating the lens position at this time. Difference from EVTCNT value T3 (= T3 ₁ ) SERR
-Given at T3. Accordingly, the lens movement amount ITI within the focus detection time of one cycle is obtained by subtracting the value (MI-DT) obtained by subtracting MI by DT from the MIL. That is, ITI = MIL- (MI-DT).

In steps S512 and S513, the DT
And ITI are calculated, the value T3 of the event counter EVTCNT at the end of the current calculation is read in step S514. Then, the time TM3 at the end of the calculation is read in step S515, and thereafter, the process proceeds to step S7 in FIG. Now, FIGS. 6 and 7 are the same as FIG.
3 is a flow in which the flow after the determination whether the lens is stopped or being driven in step S410 is described in detail.

FIG. 6 shows a flow chart when the lens is stopped. This mode is executed when the flow is first executed, or when the focus is confirmed or when the focus is achieved. In step S601, it is determined whether or not the lens is currently in the predetermined focusing zone. If it is in the focusing zone, the process proceeds to step S602, and the lens drive amount E obtained this time is determined.
The RR is set as the previous lens drive amount LERR for use in the next correction, and the lens drive set value EVTCNT obtained this time is similarly set to SERR. In step S603, the defocus direction obtained this time is similarly rewritten with the previous result,
Then, in step S604, together with the in-focus display as described later, the display circuit 115-2 displays the distance to the subject.
(Details will be described later) is performed, and thereafter, the process returns to step S6 in FIG. 3 and the focus detection is repeated again.

On the other hand, if it is determined in step S601 that the flow is out of the focusing zone, the flow advances to step S605 to determine whether the flow is executed for the first time. If it is the first execution, the flow advances to step S606 to set the follow flag. Will be reset. This tracking flag is used to determine whether or not to enter the tracking mode in which correction is performed to improve the tracking of focus detection. In step S606 ′, the past data WR (1), WR (2), LW (1) used for the filtering process described later are reset. Then, in step S607, the non-update flag that prohibits updating of the count value of the event counter EVTCNT is reset, and in the next step S608, the tracking correction flag that sequentially corrects the calculation result obtained in the tracking mode is reset to 0. .

When the flow is executed next time, step S60
5 to steps S610, S611, S612,
The defocus direction obtained by the previous calculation result and the current defocus direction are compared. If the direction is reversed,
In step S613, the backlash of the lens driving system is corrected, and then the process proceeds to step S606, and the follow-up flag is reset as an initial setting. This means exiting this mode if it is the follow-up mode. On the other hand, if the defocus directions are the same, step S61.
In step 4, the amount of movement WR of the subject is calculated. This calculation method will be described with reference to FIG.

The vertical axis represents the focal position of the lens, and the horizontal axis represents time. In the figure, A ₁₆ indicates a true change of a moving subject, B ₁₆ indicates a lens driven so as to follow the subject, and the mutual distance intervals at the same point indicate the defocus amount. There is. At the time TM3 at which the calculation C ₃ is finished, the movement amount WR of the object detected in one cycle between the integration central points TMIL and TMI of the previous integration I ₂ and the current integration I ₃ has already been obtained. hand,
Further, the defocus amounts DFb and DFc at the central points TMIL and TMI of the integrals I ₂ and I ₃ are also obtained. The driving amount of the lens of TMI is TTI from TMIL. And the central point TMIL integral I _2, the center points of the integration I ₃ TM
From the figure, the defocus amount WR caused by the movement of the subject detected during this period is WR = ITI + DFc-DFb. Where DFc is the defocus amount this time,
In step S409, ERR is set in pulse count units, DFb is the previous defocus amount, and in step S624, LEER is set in pulse count units. Therefore, the above equation is calculated as WR = ERR + ITL-LERR.

Next, filtering is performed. An example of the filtering process in step S614 'of FIG. 6 is shown in FIG.

In the focus detection, generally, the detection value varies due to the noise of the CCD image sensor 107 or the noise of the circuit. That is, step S61
Since there are variations in the values of ERR and LERR in 4, the obtained defocus amount WR also includes variations. Therefore, if correction is performed with this defocus amount WR, stable control cannot be performed due to variations and a problem occurs in AF accuracy. Therefore, in order to absorb this variation, the average value of past detection data is taken into consideration. That is, in step S1401, the change amount WR (0) of the defocus amount per unit time is calculated by calculating WR / (TMIL-TMI). This change amount WR (0) indicates the speed of the defocus of the subject in the optical axis direction. In the next step S1402, it is determined whether or not the value of the change amount WR (0) is larger than a predetermined value HS. If the moving speed of the subject is high and the change amount WR (0) is larger than the predetermined value HS, the step S1402 is performed. In step S1403, the averaged variation amount LWR (0) is calculated by the following equation from the variation amount LWR (1) obtained by the previous computation described in step S1404 and the variation amount WR (0) this time. It

[0039]

[Formula 1] LWR (0) = (LWR (1) + WR (0)) / 2

Then, in step S1404, the current calculation result LWR (0) is set as LWR (1) to be used as the previous data in the processing of the next cycle. On the other hand, the moving speed of the subject is small and the change amount W
If R (0) is smaller than the predetermined value HS, step S1
405, the averaged change amount LWR is calculated by the following equation.
(0) is calculated, and the process proceeds to step S1404.

[0041]

[Equation 2] LWR (0) = (3 · LWR (1) + WR0) / 4

Therefore, the averaged change amount LWR (0) obtained in step S1403 includes past data in the relationship shown by the equation, and similarly, step S1405.
The averaged change amount LWR (0) obtained in the above step includes the past data in the relationship shown in the equation.

[0043]

[Equation 3]

[0044]

[Equation 4]

WR (i) is the defocus amount WR before i times
, And since this filtering is linked to the ranging cycle, the value of i is finite. Comparing the above two equations, the first equation shows that the specific gravity of the past data is smaller than that of the first equation. That is, when the formula is adopted, the data at the present time is emphasized, and therefore the responsiveness is excellent. On the other hand, when the formula is adopted, the past data is emphasized. It is advantageous to absorb the variation.

Description will be made with reference to FIG. In FIG. 20, the vertical axis represents the change speed of the defocus amount, and the horizontal axis represents time. The change speed of the focal position due to the movement of the true subject is indicated by A ₁₇ . By performing a large filtering specific gravity of past data shown here in the formula, the subject as shown in B ₁₇ is detected to come moved. That is, the accuracy is high and stable in the area D where the moving speed of the object is small, but the response delay occurs in the area E where the moving speed of the object changes greatly. If the new data represented by the formula is filtered with a large specific gravity, the responsiveness is good although it is not stable as shown in C ₁₇ . That is, In the region of D, the filtering of the second formula is more advantageous in terms of accuracy and stability, and in the region of E, the filtering of the formula of good response is advantageous.

That is, when the moving speed of the object is small, the first formula is adopted, and the past data for which the average data is obtained is emphasized, so that the variation is absorbed and more accurate data is obtained. can get. On the other hand, when the subject moves abruptly, the first formula is adopted, and the data obtained at this moment is emphasized over the past data to improve the responsiveness and follow the subject moving at high speed. It will be possible.

Since the focal position of the lens is almost inversely proportional to the subject position, it is inversely proportional to time when the subject moves at a constant velocity in the optical axis direction. Further, the changing speed of the focal position of the lens is inversely proportional to the square of time, and thus changes rapidly. Therefore, it is extremely effective to switch the filtering means in this way.

Although the change amount WR (0) is compared with the constant value HS in step S1402, it may be compared with the previous averaged change amount LWR (1). Further, as shown in the above formula, the past data may not be exponentially averaged, but a simple weighted average may be adopted as shown in FIG. That is, when the change amount WR (0) of the subject movement is larger than the predetermined value HS, the process proceeds to step S1406, and the average change amount LW is calculated by the following equation.
R (0) is calculated.

[0050]

[Formula 5] LWR (0) = (3 · WR (0) + 2 · WR (1) + WR (2)) / 6

WR (1) and WR (2) are the amounts of change in the previous time and the time before the last time, respectively. On the other hand, the change amount WR of the subject movement
If (0) is smaller than the predetermined value HS, step S1
407, the averaged change amount LWR is calculated by the following equation.
(0) is calculated.

[0052]

[Equation 6] LWR (0) = (8 ・ WR (0) +7 ・ WR (1) +6 ・ WR (2)) / 21

That is, the formula (1) is similar to the formula (1) above and is excellent in responsiveness, and the formula (3) is also excellent in stability as in the formula (1). Then, in step S1408, the previous change amount WR (1) is set as the change amount WR (2) of the previous two times. In step S1409, the calculated change amount WR (0) is set as the previous change amount WR (1).

16 and 17 show another embodiment of the filtering process. 16
In the process in FIG. 14, the determination of the magnitude of the movement amount WR (0) of the subject is not made, but the averaged movement amount LWR (0) is calculated with an emphasis on stability. In FIG. 17, the determination of the magnitude of the movement amount WR (0) of the subject is not performed, and the data WR (0) to WR (previously before) is calculated in step S1410.
The averaged moving amount LWR (0) is calculated by the weighted average of (2). In this case, similar to step S1407 of FIG. 15, weight may be added to the past data. That is, the calculation in step S1410 may be performed by the following equation.

[0055]

[Formula 7] LWR (0) = (n · WR (0) + m · WR (1) + 1 / WR (2)) / (n + m + 1)

Although the past two data are used here, more past data may be used depending on the processing time and the capacity of the microcomputer 109. Further, instead of filtering the defocus speed WR (0) of the subject, the defocus amount WR due to the movement of the subject may be used.
Alternatively, you can filter the focus detection value itself,
Then, the defocus speed of the subject may be calculated.
Further, when the filtering means that attaches importance to the data at the present time is selected, it indicates that the subject is moving at a high speed, and therefore it is preferable to control the lens driving motor at a higher speed.

Returning to FIG. 6, in the next step S615, the state of the follow flag is determined. The operation will be described in accordance with the flow of this flow.
Since the follow-up flag has been reset by the execution of the first time, the process proceeds from step S615 to step S616 this time. Here, the magnitude of the averaged movement amount LWR (0) is determined. The predetermined value AB described here is a value set to the defocus speed that is regarded as the focus zone without performing the follow-up correction in consideration of the variation in the calculation result and the width of the focus zone.

Now, the averaged movement amount LWR (0) is the predetermined value A.
If it is less than B, the process proceeds to step S607, but if the averaged movement amount LWR (0) is greater than or equal to the predetermined value AB, step S61.
After the follow-up flag is set to 1 in step 7, step S6
Proceed to 07.

At the time of executing the next flow in this case, the follow-up mode is set by setting the follow-up flag, and therefore, steps S601, S614, S615 and S6 are executed.
Proceed to 18. Here, as in step S616, the averaged movement amount LWR (0) is compared with the predetermined value AB, and the LWR
If (0) is less than the predetermined value AB, follow-up correction is not performed and the process proceeds to step S607. If LWR (0) is equal to or more than the predetermined value AB, the process proceeds to step S619. Here, the movement amount WR of the subject is compared with another predetermined value AX that is considerably larger than the predetermined value AB, and if WR is less than AX, the non-update flag is reset in step S621 and the following correction is performed in step S622. Flag is set.

On the other hand, when the movement amount WR is AX or more, the non-update flag is set in step S623, and thereafter, the process proceeds to step S608 to reset the tracking correction flag. This flow is when the movement amount WR of the subject largely changes due to the change of the camera direction during the follow-up mode. In this case, the event counter EVT
CNT is not updated, the previous counter value remains as it is, tracking correction is also prohibited, and A
F control is performed, and for this reason, follow-up correction is also prohibited. In addition, here
Since the value WR before the filtering is used, the response is not delayed by the filtering, and the detection can be performed at high speed.

At the time of executing the next flow, the value that has largely changed is replaced as the lens drive amount LERR. At this time, if the orientation of the camera remains changed, the movement amount WR of the subject will not change greatly this time. In steps S621 and S622, the non-update flag is reset and the tracking correction flag is set.

In this way, when the defocus amount changes significantly, the calculation result at this time is ignored once, and AF control is performed with the previous data, and the orientation of the camera also changes thereafter. If this is left, the movement amount WR of the subject becomes less than AX this time, and step S62
By advancing to 1, the AF control is performed thereafter with the lens drive amount LERR that has changed greatly.

After step S608 and step S622, the process proceeds to step S624, and the lens drive amount E this time.
The RR is replaced with the previous data LERR, and in step S625, the defocus direction obtained this time is replaced with the previous direction. And step S62
The tracking correction flag is determined in 6 and the tracking correction flag is set to 1
If it is set to, the tracking correction, which will be described in detail later, is calculated in step S627, and the value of the lens drive amount ERR is corrected. Therefore, in step S624, the lens drive amount LERR that has not been subjected to follow-up correction is stored as the previous lens drive amount LERR. Next, if the follow-up flag is set to 1 in step S628 (the subject is a moving object), in-focus determination is made in step S629 as to whether or not it is within a follow-up focusing zone, which will be described later, and it is within the focusing zone. Then, in-focus display and distance display are performed in step S630, and thereafter, the process proceeds to step S424 in FIG. On the other hand, if the follow-up flag is reset in step S628 and if it is outside the focus zone in step S629, the focus determination is not performed and the process proceeds to step S424. The tracking focus zone mentioned above is a zone that may not be in the focus zone at the end of the current calculation, but the effect of tracking correction will appear at the timing after this, and it will be in the focus zone. Is displayed even when the lens is being driven.

FIG. 8 is a detailed description of the calculation contents of the tracking correction in step S627, and this correction method will be described with reference to FIG.

At the time TM3 at which the calculation C ₃ is finished, as described above, the movement of the object for one cycle between the integration central points TMIL and TMI of the previous integration I ₂ and the current integration I ₃ is completed. The amount WR has already been obtained, and the defocus amount DFc at the central point TMI of the integral I ₃ has also been obtained. However, in the figure, the line A ₁₈ indicates the true movement of the subject, and the detected defocus amount has an error due to electrical noise, dark output, or the like as described above. Here, the defocus amount in the integrals I ₁ , I ₂ , and I ₃ is D Fa,
Assuming that DFb and DFc are obtained as shown in the figure, the subject movement amount WR naturally has an error. Time point TM
_The subject movement amount WR detected in ₃ indicates that the subject is moving as indicated by a straight line C ₁₈ , and the line A indicating the true movement.
_A large error is generated compared to ₁₈ . In the present embodiment, as described above, filtering is performed and variations in the detection results are absorbed, so that detection is performed as indicated by the straight line D ₁₈ , for example, and errors can be suppressed. This will be described in more detail with reference to FIG.

In FIG. 22, the vertical axis represents the defocus amount and the horizontal axis represents time. A true movement of the subject
₁₉ , the defocus detection value is indicated by a white circle. It is assumed that the lens is stopped for the sake of simplicity. In the figure, if the defocus change of the object is detected at the detection values at the integration points I ₂ and I ₃ at the time point TM3, the variation in the detection values at these two points is directly affected, and is indicated by C ₁₉ . As a result, it is determined that the subject is moving. If the filtering is performed, the detection value obtained by the integration before the integration I ₂ is also used for detecting the defocus change. That is, since the detection value of the time integral I _-5 ~I ₃ are averaged, is detected as shown by the straight line D ₁₉ ', it is possible to suppress the occurrence of errors. The slope of the straight line D ₁₉ 'indicates the averaged movement amount LWR (0). The straight line D ₁₉ is a straight line having the same inclination as the straight line D ₁₉ ′ and passing through the detected value of the integral I ₃ , and corresponds to the straight line D ₁₈ in FIG. Returning to FIG. 21, since the subject further moves during the subsequent driving of the lens, it is meaningless to correct the defocus amount with this time TM3 as a target. Therefore, the time TM3 ′ at which the next integration I ₄ and the calculation C ₄ are finished and a new defocus amount DFd is calculated.
It can be said that it is an efficient and appropriate correction to correct with the target. For this reason, it is sufficient to correct the relative movement amount X of the subject between the time point TMI that is the actual defocus amount DFc and the time point TM3 ′. Time TMIL to T
The moving speed of the object in MI is L as described above.
It is calculated by WR (0).

The amount of movement of the subject from the time TMI to the time TM3 is (TMI-TM3) × LWR (0), and if the focus detection cycle is made almost constant and TM3-TM3 '= TMIL-TMI is approximated, The moving amount of the subject from TM3 to TM3 ′ is (TMIL−TMI) × LWR (0). Therefore, the time TMI
The amount of movement X of the subject from the time to TM3 ′ is X = {(TMIL−TMI) + (TMI−TM3)} × LWR (0) = (TMIL−TM3) × LWR (0).

The obtained amount of movement X of the subject is set as the correction amount SWR in step S627-1, and the lens drive amount ERR is corrected with this correction amount SWR in the next step S627-2.

Although the case where the lens catches up with the moving subject is described here, the same control as above is performed even when the subject moves in the moving direction of the lens. It FIG. 9 shows the display routine of steps S604 and S630 in FIG.

In step S901, the distance counter DSCN is set to the sum of the count value of the lens feed amount absolute counter LNSC and the lens drive amount ERR. This lens extension amount absolute counter LNSC
Is a counter that is 0 when the lens is in the ∞ position and counts in proportion to the amount of lens extension. Therefore, a count value corresponding to the distance to the subject is input to the distance counter DSCN. In step S902, the count value of the distance counter DSCN is multiplied by the distance conversion data Dkl peculiar to the lens input from the lens and converted into data called display parameter DSPS. Although this data is not distance data, it is sent to the display device to become distance display data, and the distance is displayed in step S903.

Returning to FIG. 4 again, the operation when it is determined in step S410 that the lens is being driven will be described in detail with reference to FIG.

In steps S701 to S703, the driving direction of the lens and the defocus direction after the movement amount correction are compared. If the directions are reversed, the process proceeds to step S704, and the tracking flag is reset. This means that the lens catches up with the subject during the follow-up operation and overtakes as it is, so that the follow-up mode is released. Then, step S70
4'in the past data WR (1), WR (2), L already described
After WR (1) is cleared and the driving of the lens is stopped in the next step S705, the process returns to step S6 in FIG. 3 and the distance measurement calculation is performed again. On the other hand, if the driving direction of the lens is the same as the previous driving direction, step S706.
Then, as described above, the movement amount WR of the subject is calculated by ERR + ITI-LERR. Then, in step S706 ',
Similar filtering processing is performed. In the next step S707, it is determined by the flag whether or not the follow-up mode is set. If the follow-up mode is set, steps S708 to S7 are performed.
14, the description is omitted because this part is the same as step S618 and subsequent steps in the stopped mode of FIG.

On the other hand, if the tracking mode is not set, step S
In step 715, it is determined whether the averaged movement amount LWR (0) is larger than the predetermined value AB which is slightly smaller than the predetermined value AB. If smaller, the process proceeds to steps S712 and S714.
If the non-update flag and the follow-up correction flag are reset, and the averaged movement amount LWR (0) is equal to or greater than the predetermined value AA, the follow-up flag is set in step S716, and thereafter, in step S711 and S713, The update flag is reset and the tracking correction flag is set. This point is different from the stopped mode, and in the lens moving mode, high-speed control is required, so that the follow-up correction flag is set so that the follow-up correction is performed immediately. After step S713 and step S714, the process proceeds to step S624 in FIG.

FIG. 10 shows step S424 in FIG.
~ It is a detailed description of S427. First step S
If the state of the non-update flag is determined in 1001 and the flag is reset, the process proceeds to step S1002, and it is determined whether the lens is currently being driven. If the lens is being driven, in step S1003, the subject data of Lens movement amount CTC (= MI-T from the time of acquisition to the end of calculation)
3) is calculated, and the drive amount ERR of the lens is corrected in step S1004. That is, the lens movement amount CTC, which is a count error between the data input time and the time when the calculation end result is obtained, is corrected, and then the process proceeds to step S1005. If the lens is not being driven, steps S1002 and S1003 are skipped. In step S1005, it is determined whether or not the lens drive count value ERR is in the near zone NZC. If it is in the near zone NZC, in step S1006 the lens drive is set to a low speed in order to improve focusing accuracy. The newly obtained lens drive count value ERR is set in the event counter EVTCNT. on the other hand,
If it is outside the near zone NZC, step S1007.
At, the high speed is set, and the lens drive count value ERR is set in the event counter EVTCNT. In step S1008, the event counter EVTCNT is calculated to calculate the offset of the next event count.
Is set as the lens drive amount SERR. After the AF driving motor is energized in the next step S1009, the process returns to step S6 in FIG.

FIG. 11 shows an interrupt routine for controlling the lens drive amount, and this routine is executed every time a pulse is output from the encoder along with the rotation of the motor.

First, in step S1101, 1 is subtracted from the event count value indicating the lens drive amount. In step S1102, it is determined whether the event count value becomes 0 and driving of the target lens drive amount is completed. If it becomes 0, the motor is stopped in step S1103, and then the process returns. After the return, if the calculation result during the stop is within the focus zone, the focus display is performed.

FIG. 12 shows an interrupt routine which is generated when the switch S ₂ is turned on by pushing the release button while the AF routine of FIG. 3 is being executed.

In step S1201, it is determined whether the tracking mode is set. If the tracking flag is set, the tracking correction of the lens drive amount is calculated in step S1202, and based on the correction result until the start of exposure. The lens is driven. In this correction, the event counter EVTCNT is corrected for the amount of movement of the subject even during the release time lag from the release signal being input to the start of exposure. If the tracking correction flag is reset, driving of the lens is stopped in step S1203. This is because the lens is relatively close to the subject during the follow-up mode, so it is controlled at a low speed, but in the normal mode that is not the follow-up mode, there may be a high speed, in which case the lens is stopped. Even if a signal is issued, it takes a little time to completely stop and a delay of up to a release time lag occurs at maximum, so the lens is stopped unless in the follow-up mode.

Here, the follow-up correction calculation during release in step S1202 will be described with reference to FIG.
In step S1301, RT is a release time lag time specific to the camera and is a constant value. LWR
(0) is the filtered defocus amount of the subject per unit time, and therefore LWR (0) ·
RT represents the follow-up delay amount during the release time lag, and this value is the moving defocus amount SWR of the subject.
I am trying. In the next step S1302, the obtained defocus amount SWR is added to the count value of the event counter EVTCNT and corrected.

Now, returning to FIG. 12, step S1204.
At, the display showing the focused state is turned off. Subsequently, the raising of the reflecting mirror 105 is started in step S1205, and the aperture control is performed via the exposure control circuit 121 in the next step S1206. In step S1207, it is determined whether the raising of the reflection mirror 105 is completed,
Upon completion, the process advances to step S1208 to stop driving the lens. In this way, the lens drive is continued in the follow-up mode until the reflection mirror 105 moves up, that is, until the exposure is started. Step S1209 exposed in starts, whether the switch S ₅ in the next step S1210 is exposed turned on has been completed is determined. When the exposure is completed, the switch 1211 starts automatic film winding, and subsequently, in step S1212, the reflecting mirror 105 is lowered. In step S1212, state by continuous shooting mode switch S ₄ is determined whether is made, if the continuous shooting mode, step S3 in FIG. 3
Then, similar control is performed thereafter. On the other hand, in the single shooting mode, the process proceeds to a loop for repeating only photometry in steps S1214 and S1215, and waits for the next release operation or the switch S ₁ being turned off.

As described above, by performing filtering, the defocus change due to the movement of the subject can be accurately and stably corrected, and when the change in the defocus amount due to the movement of the subject is small, the past data has it. By performing the averaging process with a large specific gravity, variations can be absorbed and stable follow-up correction can be performed.When the defocus amount changes greatly, the averaging process that emphasizes the current data is performed. Because
The responsiveness is excellent, and it becomes possible to perform focus adjustment by following a subject moving at high speed.

[0082]

As described above, the first determining means for determining whether or not the taking lens is being driven, the second determining means for determining whether or not the subject is a moving body, and the taking lens are A third determination means for determining whether the focus position is present,
When the first determining unit determines that the taking lens is being driven, and when the second determining unit determines that the subject is a moving object, the third determining unit performs focus determination, but determines that the object is not a moving object. When it does, the focus determination is not performed. According to this configuration, even when the moving subject is to be focused on following the object, it is possible to prevent the conventional focus determination from not being performed forever. Therefore, it is possible to prevent missing a photo opportunity even in a focus priority camera.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a block configuration of a camera to which an automatic focus adjustment device of the present invention is applied.

FIG. 2 is a block diagram showing a control circuit in FIG.

FIG. 3 is a flowchart showing the control operation in FIG.

FIG. 4 is a flowchart showing a control operation in FIG.

5 is a flowchart showing a control operation in FIG.

6 is a flowchart showing the control operation in FIG.

7 is a flowchart showing the control operation in FIG.

FIG. 8 is a flowchart showing a control operation in FIG.

9 is a flowchart showing the control operation in FIG.

FIG. 10 is a flowchart showing a control operation in FIG.

FIG. 11 is a flowchart showing a control operation in FIG.

FIG. 12 is a flowchart showing the control operation in FIG.

FIG. 13 is a flowchart showing the control operation in FIG.

FIG. 14 is a flowchart showing the control operation in FIG.

15 is a flowchart showing another embodiment of the filtering process in FIG.

FIG. 16 is a flowchart showing another embodiment of the filtering process in FIG.

FIG. 17 is a flowchart showing another embodiment of the filtering process in FIG.

FIG. 18 is a diagram for explaining calculation of a lens drive amount.

FIG. 19 is a diagram used to explain the operation of tracking correction in an easy-to-understand manner.

FIG. 20 is a diagram used for explaining the operation of the filtering process.

FIG. 21 is a diagram used to explain an operation of tracking correction in an easy-to-understand manner.

FIG. 22 is a diagram used to explain an operation of tracking correction in an easy-to-understand manner.

[Explanation of symbols]

 101 Clutch 102 Clutch 103 Lens Circuit 104 Reading Circuit 105 Reflecting Mirror 107 CCD Image Sensor 108 Interface Circuit 109 Microcomputer 110 Slip Mechanism 111 Drive Mechanism 112 Transmission Mechanism 113 Encoder 114 Motor Driver 115 Display Circuit 121 Exposure Control Circuit 122 Photometric Circuit 124 One Piece Winding circuit 125 Exposure setting circuit MO1 motor MO2 motor S switch

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area H04N 5/232 H

Claims (1)

[Claims] 1. An optical axis of the subject on the basis of focus detection means for repeatedly calculating a defocus amount from the in-focus position of the photographing lens with respect to the subject, and a plurality of defocus amounts repeatedly output from the focus detection means. A movement detecting means for detecting movement in a direction, a calculating means for calculating a defocus amount in which a change amount of the defocus amount caused by the movement of the subject is added to the defocus amount detected by the focus detecting means, Driving means for driving the lens, first determining means for determining whether the photographing lens is being driven, and whether or not the subject is a moving body is determined based on the detection result of the movement detecting means. The second determining means, the third determining means for determining whether the photographing lens is in the in-focus position, and the first determining means determine that the photographing lens is being driven. In this case, the second determination means determines whether or not the subject is a moving body. When it is determined that the subject is a moving body, the third determination means performs a focus determination, but when it is determined that the subject is not a moving body, the focus determination is performed. An automatic focus adjustment device comprising: