JPH03226723A - Automatic focusing device for camera - Google Patents

Abstract

PURPOSE:To perform the more accurate correction of a defocusing length irrespective of the moving speed of an object by predicting the field speed of the object at the time of exposing by using high-order approximation function such as a secondary function, and calculating the focused position of a lens based on the predicted image surface speed. CONSTITUTION:The field speed of the object is repeatedly calculated by a field speed calculating means 53 based on a defocusing length calculated by a defocusing length calculating means 52. And the field speed at the time of exposing is predicted by a field speed predicting means 54 based on the calculated field speed, and then, the focused position of the photographing lens 51 is calculated by a lens position calculating means 55 based on the predicted field speed. And also, the photographing lens 51 is driven to the calculated focused position. Thus, the more accurate correction of the defocusing length can be performed irrespective of the moving speed of the object.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic focus adjustment device for a camera, and more particularly to an automatic focus adjustment device for a camera that can more accurately focus a camera.

[Conventional technology] A camera with autofocus is provided.

When the subject is a moving object, conventional cameras with automatic focus adjustment devices use a function to predict the next image plane position from the past defocus amount, lens drive amount, and current defocus amount, and then calculate the next image plane position. The lens is driven so that focusing is performed at .

[Problems to be Solved by the Invention] In a conventional camera having an automatic focus adjustment device, correction of the amount of defocus when the subject is a moving object is performed using a linear function. When the moving speed of the subject was slow, it was possible to take a focused photograph even if the defocus amount was corrected using a linear function. However, if the moving speed of the subject is fast, the camera may not be able to follow the amount of defocus and accurate correction may not be possible.

The present invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide an automatic focus adjustment device for a camera that can more accurately correct the amount of defocus regardless of the moving speed of the subject.

[Means for Solving the Three Problems] An automatic focusing device for a camera according to the present invention has a configuration as shown in FIG. 1 in order to achieve the above object. That is, the automatic focus adjustment device for a camera according to the present invention includes a defocus amount calculating means 52 for calculating the defocus amount of the subject, and based on the calculated defocus amount,
Image surface velocity calculation means 5 that repeatedly calculates the image surface velocity of the subject
3, and image surface velocity prediction means 5 that predicts the image surface velocity during exposure using a high-order approximation function based on the calculated image surface velocity.
4, and a lens position calculation means 55 for calculating the focal position of the lens based on the predicted image surface velocity.

However, FIG. 1 is a block diagram showing the configuration of the present invention in functional blocks, and in the embodiments described later, the main part of the above configuration is realized by a microcomputer program.

[Action Co. The operation of this invention will be explained below with reference to FIG.

Based on the defocus amount calculated by the defocus amount calculation means 52, the image surface speed calculation means 53 repeatedly calculates the image surface speed of the subject. Then, based on the calculated image surface speed, the image surface speed at the time of exposure is predicted by the image surface speed prediction means 54,
Based on the predicted image surface velocity, the focal position of the photographing lens 51 is calculated by the lens position calculation means 55. The photographing lens 51 is then driven to the calculated in-focus position.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. Note that the automatic focus adjustment of the camera will be abbreviated as AF below.

FIG. 2 is a block diagram showing the schematic 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 camera body BD. Both have clutch 1
Mechanically connected by 01.102. Clutches 101 and 102 move the interchangeable lens LZ to the camera body B.
D, the lens circuit 103 of the interchangeable lens drive unit and the reading circuit 104 of the camera body are connected to connection terminals JLI to JL5. They are electrically connected by JBI to JB5.

Referring to the right half of FIG. 2, the main body BD of the camera includes a defocus amount detection section 10 and a device for driving the lens to the in-focus position based on the defocus amount detected by the defocus amount detection section 10. It includes a lens drive section 20 and an interface circuit 108 that connects the defocus amount detection section 10 and the lens drive section 20. The defocus amount detection section 10 includes an optical system and a CCD image sensor 107. The lens drive unit 20 includes a controller 109 serving as the central part of lens drive, a motor driver circuit 114 connected to the controller 109, a slip mechanism 110 connected to the motor driver circuit 114, an encoder 113, and an encoder 113 connected to the controller. A reading circuit 104 that reads signals from the lens circuit 103, and a display circuit 11 that performs various displays.
5.

In the camera system shown in FIG. 2, the subject light that has passed through the lens system of the interchangeable lens LZ passes through the semi-transparent part at the center of the reflecting mirror 105 of the camera body BD, is reflected by the sub-mirror 106, and is reflected in the focus detection module. CC of
The light is received by the D image sensor 107. This CCD image sensor 107 is used as a distance measuring means for measuring the distance to the subject. A known CCD image sensor is used in which a plurality of photoelectric conversion elements are arranged in an array and signals from each photoelectric conversion element are sequentially extracted.

The interface circuit 108 drives the CCD image sensor, takes in object data from the CCD image sensor 107, and sends the taken data to the controller 109.

The controller 109 determines, based on the signal from the CCD image sensor 107, a defocus amount 1Δ1 indicating the amount of deviation of the lens from the in-focus position, and whether the lens position is shifted forward (front bin) or backward ( A signal with respect to the defocus direction indicating the direction of shift of the rear bin) is calculated.

The motor Mol connected to the motor driver circuit 114 is driven based on these signals, and its rotation is caused by the slip mechanism 110, the drive mechanism 111, the clutch 102 .
The signal is transmitted via 101 to the transmission mechanism 112 on the interchangeable lens LZ side. As a result, the lens system of the interchangeable lens LZ is moved back and forth in the optical axis direction, and focus adjustment is performed. At this time, an encoder 113 is connected to the drive mechanism 111 of the camera body BD in order to monitor the amount of movement of the lens system.

The encoder 113 outputs a number of pulses corresponding to the amount of drive of the lens system.

Note that the slip mechanism 110 is provided to cause the power of the motor 101 to slip when a torque of a predetermined value or more is applied to the driven portion of the interchangeable lens LZ. As a result, no unnecessary load is applied to the motor Mol.

Next, the terminal between the lens circuit 103 and the reading circuit 104 will be explained. The reading circuit 104 on the camera body side and the lens circuit 103 on the interchangeable lens side are connected to terminals JBI-JLI.
The power supply is supplied via the terminal JB2-J.The clock pulse for synchronization during data transfer is supplied via the terminal JB3-JL2.
A read start signal to start reading data is sent via L3. Serial data is sent from the lens circuit 103 to the reading circuit 104 via terminals JL4-JB4. Note that terminals JB5-JL5 are common ground terminals.

When a reading start signal is first sent to the lens circuit 103, data from the lens circuit 103 is sent to the reading circuit 104 in synchronization with a clock pulse.

The reading circuit] 04 converts the manually input serial data into parallel data KL based on the same tarok pulse as the clock pulse output to the lens circuit 10B, and sends it to the controller 109.

The controller 109 has internal data KB and the reading circuit 10.
The calculation -KL-KB is performed based on the data KL from 4. The controller 109 calculates the defocus amount 1Δ1 from the subject image data from the interface circuit 108 and determines the number N of pulses to be detected by the encoder 113.
is calculated by calculating K·1Δ. Further, the controller 109 rotates the motor Mol clockwise or counterclockwise through the motor driver circuit 114 in accordance with a signal in the defocus direction obtained from the data of the subject image. When a pulse equal to the above calculated value N is input from the encoder 113 to the controller 109, it is determined that the focusing lens system has moved by the amount of movement Δd to the in-focus position, and the rotation of the motor Mol is stopped. .

When the object is in focus through such focus adjustment, a predetermined signal is sent from the controller 109 to the display circuit 115, and the in-focus display and the distance to the subject are displayed.

This is the general operation of the camera. Next, referring to FIG. 3, the control operation in the controller 109 will be explained in more detail. In FIG. 3, the same parts as in FIG. 2 are given the same reference numerals.

The controller 109 is a microcomputer (hereinafter referred to as microcomputer). The microcomputer 109 is connected to an exposure control circuit 121 that opens and closes the shutter according to the start and end of exposure, and also performs mirror-up of the reflecting mirror 105 and aperture control in response to a mirror-up signal. [Microcomputer] 09 includes a photometry circuit 122 that digitizes a signal according to the brightness of the subject and sends it to the microcomputer 109.
is connected. Furthermore, the microcomputer 109 includes a film sensitivity automatic reading circuit 12 that reads the loaded film sensitivity.
A film one-frame winding circuit 124 for winding the film one frame by driving the motor MO2 in response to signals from the microcomputer 109 and the microcomputer 109 is connected to an exposure setting circuit 125 for setting the shutter speed and aperture value. The setting values of the film sensitivity and exposure setting circuit] 25 read by the film sensitivity automatic reading circuit 123 are taken into the microcomputer 109. Furthermore, the microcomputer 109 has a CCD as mentioned above.
The image sensor 107 is connected via an interface circuit 108. The image information of the subject obtained by the CCD image sensor] 07 is taken into the microcomputer 109. A motor driver circuit 114 and the like are further connected to the microcomputer 109 as explained in the block diagram of FIG. 2 earlier.

Next, switches connected to the microcomputer 109 will be explained. The following switches are connected to the microcomputer 109. The switch S is turned on at the first step of pressing the release button (not shown), and the microcomputer 109 is turned on by turning on the switch S, which will be described later.
Execute F flow. The switch S2 is a switch that is turned on in the second step of pressing the release button, and when the switch S2 is turned on, a release routine flow described later is executed. The switch S3 is a switch that is turned on when the reflection mirror is completely raised, and is turned off when a release member (not shown) is charged. The switch s4 is a shooting mode changeover switch for switching between continuous shooting mode and single frame shooting mode. Switch S is a switch that is turned on when exposure is completed and turned off when winding of one frame of film is completed.

The primary side of each of the switches 81 to S5 described above is grounded, and the secondary side connected to the microcomputer 109 is pulled up to voltage V via a resistor R, respectively.

Next, the control operation of the camera having the microcomputer 109 as described above will be explained according to a flowchart.

When the switch S is turned on by the first step of pressing the release button, the microcomputer 109 executes the flowchart shown in FIG.

First, in step S1, various flags are reset,
In step S2, a free run timer within the microcomputer 109 is started to notify the time of each operation.

Then, in step S3, the lens circuit 105 sends the lens through the reading circuit 104 to the focal length of the lens required for AF, the maximum aperture value, and the extension amount conversion coefficient representing the amount of movement of the lens in the optical axis direction with respect to the rotational speed given to the lens. Data such as , etc. are taken into the microcomputer 109 . In the next step S4,
The set aperture value, shutter speed, etc. are stored in exposure setting circuit 1.
25, and in the next step S5, a focus detection calculation as described later and an AF operation to drive the lens to the in-focus position based on the result of this calculation are performed. Step S
In step S6, the photometry result by the photometry circuit 122 is taken in, and in step S7, the film sensitivity is taken in by the film sensitivity reading circuit 123. In step S8, exposure calculation for exposure is performed based on the above input data, and then the program returns to step s3.

FIG. 5 is a flowchart showing the subroutine of the AF operation in step S5. Referring to Figure 5,
The AF operation subroutine will be explained.

First, in step 5401, subject light is integrated by the CCD image sensor 107 via the interface circuit 108. In the next step 5402, the object data integrated by the CCD image sensor 107 is taken out for each pixel (this operation is called data dump), A/D converted by the interface circuit 108, and then taken into the microcomputer 1.9. It will be done. In step 8403, focus detection calculations are performed using the data of the subject. Note that a detailed explanation of the optical system into which the subject light is input and the focus detection calculation is not necessary here and will therefore be omitted. The details are described in, for example, Japanese Patent Laid-Open No. 126517/1983.

In the next step 5404, preliminary calculations for tracking correction are performed as will be described later. In step 5405,
The defocus amount and its direction are calculated based on the data from the CCD image sensor 107, and it is determined from the calculation results whether or not the defocus amount can be detected. If the subject image is greatly blurred or has low contrast, it is considered undetectable and the program goes to step 540.
Proceed to step 6.

In step 5406, when the contrast is low,
It is determined whether the low-contrast scan, which searches for a contrasting area by moving the lens position and repeating distance measurement, has been completed. If the low contrast scan is not being executed, the low contrast scan is started in step 5407. If the low contrast is still low even after the low contrast scan is finished, in step 3408 the display circuit 11
A blinking display is displayed at 5a indicating that focus detection is impossible. The program then proceeds to step S6 in FIG.
Return to.

On the other hand, if it is determined in step 5405 that the defocus amount can be detected, the process advances to step 8409;
Calculated defocus amount DF and step S3 in FIG. 4
The lens drive ff1ERR (pulse count value) is calculated from the conversion coefficient for lens feeding, which is one of the lens data taken in.

ERR=DFxK In step 5410, it is determined whether or not the lens is stopped. If it is stopped, it is determined in step 5411 whether or not the lens is in focus. If the lens is in the focus position, the focus is displayed on the display circuit 115a in step S4]2, and then the program returns to the flow shown in FIG. 4 and proceeds to step S6. On the other hand, if the lens is not in focus, the program proceeds to step 84.
In step 13, it is determined whether the defocus direction found in the current execution of the routine is the opposite direction to the defocus direction found in the previous routine execution. If the defocus direction is reversed, the amount of backlash in the lens drive system that causes an error when the lens drive is reversed is corrected, and the program proceeds to step 5424. If the lens drive directions are in the same direction, the program proceeds to step 5414, where it is determined whether or not an AF drive mode that performs follow-up correction, which will be described later, is necessary. If it is determined that an AF drive mode that performs tracking correction is necessary, the program proceeds to step 54.
In step 15, the driving amount of the lens is corrected as follow-up correction.

In the next step 5416, a determination is made as to whether the tracking mode is in focus, and if it is determined that the focus is in focus, the program displays in step 5417 that the lens is at the in-focus position, and then proceeds to step 5424. .

On the other hand, if the lens is being driven in step S4]0, the program proceeds to step 5421, where the defocus direction including the current correction in step 5415 is compared with the previous defocus direction. If it is determined that the direction is reversed, driving of the lens is stopped in step 5423, and then the program returns.

The reason why the driving of the lens is stopped here is because even though the defocus direction has changed, if the distance measurement calculation is performed without moving the lens, the reliability of the distance measurement result will be low. If the defocus direction has not been reversed, the program proceeds to step 5422, where it is determined whether follow-up correction similar to step 5414 is required. If follow-up correction is necessary, the program proceeds to step 5415, but if it is not necessary, the program proceeds to step 5424.

In step 5424, it is determined whether the lens is in the in-focus area (near zone) based on the obtained defocus amount. If it is not the near zone, the program is set to drive the lens at high speed in step 5425, and if it is in the near zone, the program is set to drive the lens at low bead in step 5426. After the lens is driven at the set driving speed in step 5427, the program returns and focus calculation is performed in step S6 and thereafter.

Next, the content of tracking correction using a linear function, which is the basis of this invention, will be explained. FIG. 6 is a diagram showing the timing of follow-up correction, which is the basis of this invention. The X-axis in the figure represents time, and the Y-axis represents the amount of defocus. Referring to FIG. 6, DF is the latest defocus amount based on a predetermined lens position, DF is the defocus amount from the previous calculation based on the predetermined lens position, and similarly DF2, DF
are the two calculations before, based on the predetermined lens position, respectively.
Each shows the defocus amount three times before the calculation. To is
It shows the time from when the latest defocus DFO is determined until when the next defocus is determined. T1 indicates the time from when the defocus jiDF of the previous calculation is determined to when the latest defocus amount DFO is determined. Similarly, T2,
T, . . . indicate the time from when DF2 is determined until DF is determined, and the time from when DF is determined until DF2 is determined, respectively. volvl, v2, ■.

...indicates the defocus speed, that is, the speed of the subject on the film surface, and V is the tracking defocus correction amount ΔDF
The average speed (V-(Vo +V,
+V2+V3)/4). The tracking defocus correction amount ΔDF is determined by V·To, and the lens is driven by this value.

Here, CCD integration is performed during each time T OST +, etc.
Data dumping, DF amount calculation, and lens driving are performed.

Next, follow-up correction according to the present invention will be explained.

FIG. 7 is a timing chart of follow-up correction according to the present invention, and FIG. 8 is a flowchart showing the subroutine of follow-up correction shown in step 5415 of FIG. 5.

Referring to FIG. 7, the X-axis represents time and the Y-axis represents defocus amount, as in the case of FIG. 6. Here, DFO is the latest defocus amount based on a predetermined lens position, and DF is calculation 1 based on a predetermined lens position.
Indicates the previous defocus amount. Similarly, DF2, DF
8, DF411. , indicates the defocus amount of the calculations performed 2 times, 3 times, 4 times, etc., based on a predetermined lens position.

To indicates the time from when the latest defocus amount DFO is determined until when the next defocus amount is determined. T represents the time from when the previous defocus amount DF is determined to when the latest defocus amount DFo is determined,
T2, T8, T4, etc. are calculated after DF2 is determined until DF is determined, and after DF is determined and DF2 is
It shows the time from when DF is found until when DF3 is found. Vl, v2, (8), (2) indicate the defocus speed, that is, the speed of the subject on the film surface. The defocusing speed v7, ■2, etc. are obtained at the time of calculating DF3 by skipping every two calculations, that is, the next DF after DFs. The defocus speed V5' is a corrected defocus weighted average speed, which will be described later, and is obtained from (4), V2, and (2). The defocus correction amount ΔDF is determined from this weighted average speed and the time To.

Next, the flow of the follow-up correction subroutine according to the present invention will be explained with reference to FIG. First step 5601
The velocity of the subject on the film surface vv can be calculated using the following equation.

Hereinafter, this calculation formula will be referred to as a simple average. next step 560
2, the predetermined speed v d and the just calculated value V are compared, and if the speed is slower than this, the program 86
Flows below 03 are executed, and flows below 8609 are executed if the speed is fast.

In step 5602, if the simple average speed of the object on the film surface ■V is smaller than the predetermined speed VT, the object speed is corrected using quadratic curve approximation because there is a relatively large amount of time. It will be done. First step 560
3, it is determined whether the simple average speed of four or more objects on the film surface has been determined. If the calculated simple average speed is less than 4, the program executes flows 8609 and below because the weighted average processing described later cannot be performed, and when the calculated simple average speed is 4 or more, flows 8604 and below are executed. First, a case where four or more simple average speeds have been determined will be explained.

In step 5604, the simple average speed V■ obtained earlier is substituted into a variable V■ for performing weighted average processing, which will be described later. In the next step 5605, the recent four simple average speeds vv
4, the average value V is calculated using Vv2, vvl, and Vv4 as follows.

y,, VVI +VV2 +VV3 + VV4 This calculation formula is called a weighted average. Next Ste Tsubu 560
6, the simple average speed vV2 is substituted for the simple average speed v1, and Vv is similarly substituted for Vv2. The weighted average speed V,' is substituted for the simple average speed vv3. Next, in step 5607, the weighted average value v corrected by quadratic curve approximation,
'(-v, +α·v, 2) is obtained. Here, α is a correction coefficient, which is obtained as α-2·Δt/f·β. Here, f is the focal length and β is the imaging magnification. As shown in this flow, the simple average speed vv1 is changed to the simple average speed Vv
2 is substituted, and VV21:VV3 are substituted in the same way.

By substituting the weighted average speed V, / into this simple average speed V3, not only the latest four simple average speeds but also the previous simple average speeds are incorporated into the defocus correction calculation during tracking, and the focus It becomes possible to absorb variations in detection, increasing the accuracy of correction. next step 560
8, the defocus correction amount ΔD F−V during tracking is calculated using the weighted average velocity v,′ obtained here.

Δt is determined.

Next, a case will be described in which the simple average speed vv determined in step 5602 is faster than the predetermined speed Vd. At this time, step 5609 is executed.

In this case, the subject is moving at high speed, so it would take time to perform weighted average processing. Also, if you use the weighted average speed V, you will be using the simple average speed from before this time, so the speed calculation The response delay becomes large, and the delay in driving the lens becomes large. In this step 8609, the simple average speed is shifted. That is, the simple average speed vv
1 is substituted with the simple average speed Vv2.

Similarly, VV is substituted for VV2, VV4 is substituted for VV, and VV is substituted for VV4. For defocus correction calculation during tracking in step 5608, the simple average speed VV is substituted into the weighted average speed V. Steps 5607.8608, previously described, are then executed.

Next, a case where four or more simple average speeds v are not found in step 8603 will be explained.

In this case as well, since weighted average processing cannot be performed, step 5609 described above is executed.

Next, correction of the defocus amount by lens driving during release will be explained with reference to FIGS. 9 and 10.

FIG. 9 shows the flow of the lens drive subroutine during release, and FIG. 10 is a timing chart in that case. When switch S2 is pressed, the currently executed flow is interrupted and the release routine shown in FIG. 9 is executed.

When the release subroutine is executed, step 57
At 01, the time t from the end of the previous distance measurement calculation (indicated by A in FIG. 10) to the start of the release subroutine;
is calculated. The reason for this is that since the current defocus amount has not been determined at the time of release, the deviation from the previously determined defocus amount is to be predicted. In the next step 5702, the end point of the previous distance measurement calculation (the first
Average velocity V of the subject on the film plane at A) in Figure 0.

(Weighted average) is used to approximate the quadratic curve using the equation %, which is the velocity of the subject on the film surface at the start of the release subroutine t1 hours after the end of the previous distance measurement calculation.
I2EL is predicted. In the next step 8703, from the start point of the release subroutine (indicated by B in FIG. 10), which is predetermined using the subject velocity VREL on the film surface at the start point of the release subroutine (indicated by B in FIG. 10). The velocity of the subject V, ε, 1 on the film surface at the time when the front curtain of the shutter starts running after time t2 (indicated by C in FIG. 10) is predicted by quadratic curve approximation.

These predicted object velocities on the film plane VREL
Correction of lens drive amount during release using %VRELI and times t1 and t2 ΔDF2-VRE L' j
+ +VRE L I ” j2 is calculated.

The sum of this lens driving amount correction ΔDF2 during release and the current defocus amount ΔDF, ΔDF+ΔDF2, becomes the defocus correction amount that must be corrected after the release subroutine is started (S705).

Thereafter, normal release processing is performed.

For reference, FIG. 10 also shows data when the tracking correction (linear function correction) that is the basis of this invention is performed.
It is shown as DF2'. Compared to linear function correction,
It can be seen whether the correction according to the present invention is better able to follow defocus changes of the subject.

FIG. 11 is a diagram showing an example of correction of defocus speed when correction is performed using a conventional method and quadratic curve approximation. Here, the X-axis shows time, and the Y-axis shows the amount of defocus from infinite speed. (1) and (3) are examples where correction is performed using a conventional linear function, and (2) and (4) are examples where correction is performed using a quadratic curve according to the present invention. Shown on the left (
1) and (2) show the case where the subject is moving at low speed, and (3) and (4) shown on the right side show the case where the subject is moving at high speed. In the figure, the solid line represents the movement of the subject, and the dotted line is the data when tracking the subject while performing defocus speed correction.The variation in the Y-axis direction is the data from infinity, including the variation in lens position due to correction drive. Indicates focus variation.

Comparing (1), (3), (2), and (4) in Fig. 11, it is found that the approximation using the quadratic function according to the present invention is superior to the case of approximation using the conventional linear function. It can be seen that the correction follows the actual movement of the subject regardless of the movement speed of the subject, perhaps due to approximation.

Furthermore, comparing (1), (2) and (3), (4),
Conventionally, if the subject speed was slow, the correction amount would follow the actual movement of the subject, but if the subject was fast, it could not be followed.

However, according to the present invention, the correction value follows the movement of the subject in both the low speed range and the high speed range.

In the embodiment of the present invention, the image surface velocity correction calculation formula is switched depending on whether the moving speed of the subject is faster or slower than a predetermined speed. It goes without saying that the image surface velocity correction calculation formula may be changed in multiple stages depending on the moving speed of the subject.

[Effects of the Invention] As described above, according to the present invention, the image plane velocity of the subject at the time of exposure is predicted using a high-order approximation function such as a quadratic function, and the predicted image plane velocity is also used. The focal position of the lens is then calculated. As a result, it is possible to provide an automatic focus adjustment device for a camera that can more accurately correct the amount of defocus regardless of the moving speed of the subject.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the main parts of this invention, and the second
FIG. 3 is a schematic block diagram of a camera to which the automatic focus adjustment device according to the present invention is applied, and FIG. 3 is a block diagram around the microcomputer of the camera to which the automatic focus adjustment device according to the present invention is applied. FIG. 4 is a flowchart showing the main flow of the automatic focus adjustment device according to the present invention, FIG. 5 is a flowchart showing the AF operation subroutine, FIG. 6 is a timing chart of conventional tracking correction, and FIG. 8 is a timing chart of tracking correction according to the present invention, FIG. 8 is a flowchart showing a tracking correction subroutine according to the invention, and FIG.
FIG. 10 is a flowchart showing the release routine, FIG. 10 is a timing chart for explaining lens drive during release, and FIG. 11 is a diagram for explaining the effect of the automatic focus adjustment device according to the present invention. . 51 is a photographing lens; 52 is a defocus amount calculation means; 5
3 is an image surface velocity calculation means, 54 is an image surface velocity prediction means, 55
is lens position calculation means, 101.102 is clutch, 1
03 is a lens circuit, 104 is a reading circuit, 109 is a controller, 110 is a pickpocket mechanism, 111 is a drive mechanism,
112 is a transmission mechanism, 113 is an encoder, 114 is a motor driver circuit, and 115 is a display circuit. 1st figure 1

Claims (1)

[Scope of Claims] Defocus amount calculating means for calculating a defocus amount of a subject; and an image plane for repeatedly calculating an image surface velocity of the subject based on the defocus amount calculated by the defocus amount calculating means. speed calculating means; image surface speed predicting means for predicting the image surface speed at the time of exposure of the subject using a high-order approximation function based on the image surface speed at the time of the start of release; and the predicted image surface speed. An automatic focus adjustment device for a camera, including a lens position calculation means for calculating a lens position based on speed.