JPH06217179A - Camera - Google Patents

Abstract

PURPOSE:To improve the precision of zoom tracking control by operating the zoom tracking control based on the recognition of a photographing operational history related with the selection of a tracking curve or the correction and arithmetic operation of a lens position, in a process that the photographing operation is repeatedly performed. CONSTITUTION:When the operation signals of zoom switches 12 and 13 are inputted through a zoom switch detecting block 14 to a zoom lens driving block 8, the block 8 drives a zoom lens 2 based on the operation signal. At the same time, the operation signals of the switches 12 and 13 are also inputted to a zoom tracking control block 7. The zoom tracking control block 7 recognizes the history of an AF operation until now by an incorporated operational history recognizing means. Simultaneously, the zoom tracking control block 7 recognizes the change of magnification by an incorporated comparing means, and selects the tracking curve to be applied to the zoom tracking control at present from the zoom tracking curve data stored in a memory 15, and a focus lens 4 is driven.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera, and more particularly, to a camera which performs a so-called zoom tracking control for moving a focusing lens (a so-called focus lens) to an appropriate position in a zooming operation of a zoom lens. .

[0002]

2. Description of the Related Art Conventionally, in many video cameras and the like, the zoom tracking operation is performed during the zooming operation of the zoom lens. FIG. 8 is a zoom tracking curve showing a change in the focus lens position which is the proper focus position with respect to the zoom lens position in the zoom tracking operation. The tracking operation is
For each zoom lens position, the focus lens is moved along the curve of FIG.

As a zoom tracking control method using the zoom tracking curve shown in FIG. 8, various methods have been conventionally proposed. For example, "NATIONAL TECHNIC
AL REPORT "(VOL. 37 NO.3 JUN. 1991, P338-344)
The zoom tracking method for the zoom lens of the video camera described in, reads the table of the zoom tracking curve stored in the memory and calculates the appropriate movement amount of the focus lens by interpolating the table,
Tracking is performed.

The zoom tracking method based on the above table interpolation will be described in detail. FIG. 9 shows a reference object distance L1 of the zoom tracking curve shown in FIG.
(= ∞) and the subject distance L2, and further, a tracking curve for the subject distance L3 interpolated between the distances L1 and L2. Zooming position Za
The focus lens positions for the subject distances L1 and L2 in A are set to A1 and A2, and the focus lens positions for the subject distances L1 and L2 in the zooming position Zb are set to B1 and B2. It is assumed that these data are stored in the memory. Then, the positions A2 and B2
As shown in the figure, the amount of feeding at is the values Db and Dd.

Now, it is assumed that the zoom lens is located at the position Za and the focus lens is located at the position A3 on the tracking curve of the object distance L3. The position A3 is the focus lens position A1, relative to the zoom position Za.
The amount of extension Dd of A2 and the focus lens position A
It can be relatively defined from the delivery amount Da of A1 and A3. Therefore, it is assumed that the zoom lens position changes to Zb. Assuming that the tracking curve of the object distance L3 changes so as to maintain a constant value of the feed ratio Da / Dd, which is the ratio of the feed amount by the focus lens positions A1 and A2, the feed amount from the position B1. Dc is obtained, and as a result, the position B3 is obtained. The feed ratio Da / Dd, which is a constant value, corresponds to the reference value of the tracking interpolation calculation applied to the embodiment described later.

The calculation by the table interpolation is premised on that a certain tracking curve is interpolated at a constant ratio with respect to the two tracking curves sandwiching it. Therefore, it is necessary to set the number of tracking curves to be stored in the memory so as to maintain the accuracy of interpolation.
As an example, a video camera has been proposed that stores eight tracking curves as data. As a proposal other than this video camera, "MITSUBISHI ELE
The camera proposed in "CTRIC ADVANCE" (DEC, 1991, P32-33) stores 12 tracking curves as data.

By the way, a camera manufactured as an actual product usually includes variations in manufacturing of the lens and the lens frame. Due to the variation, FIG.
A range shift occurs between the zoom tracking curves drawn by the two broken lines. Adjustment of the lens position is one of the measures for the deviation correction. For example, in the case of an inner focus lens, when the position of the first lens group is moved, the shape of the tracking curve does not change much on the wide side, but changes greatly on the tele side. You can adjust the curve to. As another method, it is also possible to electrically adjust the zoom lens position detection system including the zoom encoder. In general, since zoom is often used at the wide end and the tele end, the above adjustment is often performed at the wide end and the tele end. On the other hand, considering the phenomenon shown in FIG. 9 above, since the distance between the tracking curves is narrow on the wide side and relatively wide on the tele side, the selection accuracy and the reference value of the tracking curve to be applied to the zoom tracking control are It is understood that the accuracy is relatively better on the tele side.

[0008]

However, in the conventional zoom tracking control, the selection of the tracking curve, the calculation of the reference value, and the like recognize the object distance even when the photographing operation (or the photographing preparation operation) is repeatedly performed. The selection of zooming, zooming, etc., was performed regardless of the operation history (course) up to the time when the shooting was performed. Therefore, the zoom lens position may be set relatively on the telephoto side in the process of repeating the photographing operation (or the photographing preparation operation), which is advantageous in accuracy in selecting the tracking curve and obtaining the reference value at this point. Even if these conditions can be achieved, these will not be reflected in the next shooting at all, so overall there is a problem that the accuracy of zoom tracking control cannot be fully improved. It was

The present invention has been made in view of the above points, and in the process of repeatedly performing the photographing operation (or the photographing preparation operation), the tracking curve selection and the lens position correction calculation are relatively accurate. When it ’s done well,
It is an object of the present invention to provide a camera of this type in which zoom tracking control, which is advantageous in terms of accuracy, is performed based on the recognition of the shooting operation history regarding these.

[0010]

A plurality of zoom tracking curve data representing an appropriate position of the focusing lens for maintaining a focus state according to a change in magnification of the zoom lens is held under a constant object distance. Zoom tracking curve data holding means, operation history recognition means for recognizing the history of operations related to the autofocus means from the time before the present time to the present, and the current value of the magnification of the zoom lens is compared with the immediately preceding value. For selecting the zoom tracking curve data to be applied according to the recognition means by the operation history recognition means and the comparison result by the comparison means, or for obtaining the proper position of the focusing lens along the zoom tracking curve data. With reference value selection means for selecting the reference value for interpolation calculation And it said that there were pictures.

[0011]

[Operation] The history of the autofocus operation from the time before the present time to the present is recognized by the motion history recognition means,
The comparison means recognizes whether the current value of the zoom magnification is changed based on the comparison with the immediately preceding value, and selects and interpolates the tracking curve to be applied to the zoom tracking control at the present time according to the recognition. A reference value is selected in the calculation.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of the essential parts of a video camera according to an embodiment of the present invention. The main configuration of this camera is a first lens group 1 which is a fixed lens group which is a zoom lens system of four groups, a zoom lens 2 which is a second lens group for zooming, a third lens group 3 which is a fixed lens group, Focus lens 4 of the fourth lens group and CC for converting an image of subject 20 into an electric signal
D5, a video circuit block 6 which converts the image pickup signal of the CCD 5 into a video signal and outputs the video signal to a recording circuit (not shown), zoom switches 12 and 13 for instructing a zoom operation in the tele and wide directions, and the zoom switch A zoom switch detection block 14 for recognizing that the zoom switch has been pressed by the output signals of 12 and 13 and the zoom direction;
A memory 15 which is a zoom tracking data holding means of a design value and is composed of EERPOM or the like; and the zoom tracking control block 7 for performing zoom tracking control based on signals from the zoom switches 12 and 13.
The zoom lens drive block 8 that drives the zoom lens 2 based on the signal of the zoom switch, the zoom encoder 9 that detects the amount of movement of the zoom lens 2 and inputs the signal to the zoom tracking control block 7, and the zoom The focus control circuit 7 is a drive block that drives the focus lens 4 based on the outputs of the tracking control block 7 and the AF control block 10. Focus detection information indicating the degree of focus included, for example, contrast information in the hill climbing focus method, is extracted, and an AF (autofocus) control signal of the focus lens is output to the focus lens drive block 11. Control block 10
Etc.

In the present embodiment, the third lens group 3 is fixed, but the focus lens 4 may be moved in accordance with the function of the zoom lens 2. Further, the moving position of the focus lens 4 does not need to be detected because the drive block 11 is composed of a stepping motor, so that an encoder for the focus lens is unnecessary. The zoom tracking control block 7 has built-in maximum deviation information recognizing means for recognizing first information and second information, which will be described later, and calculating means for calculating a correction value for the deviation amount of tracking data. The memory 15 also stores the first information, the second information, and the like in addition to the zoom tracking data of the design value.

Next, in the zoom tracking control by the camera of the present embodiment configured as described above, it is assumed that the conventional table interpolation method is used in combination, and the deviation amount at that time is also corrected at the same time. . The zooming action is
This is executed based on the operation signals of the zoom switches 12 and 13 for tele and wide. That is, when the signal is input to the zoom lens drive block 8, the drive block 8 drives the zoom lens 2 based on the operation signal.
When the zoom encoder 9 detects that the zoom lens 2 has reached the wide or tele end, the drive block 8 stops its driving operation. At the same time, the operation signals of the zoom switches 12 and 13 are also input to the zoom tracking control block 7 and the tracking control described later is performed, and the focus lens 4 is extended to an appropriate position corresponding to the zoom position.

Further, the focusing operation of the focus lens 4 itself is executed in accordance with the focus detection information extracted from the video signal in the AF control block 10. That is,
The AF control block 10 calculates the focus position of the focus lens 4 based on the focus detection information, and the focus lens 4 is driven to the focus position via the focus lens drive block 11.

Next, the zoom tracking control of the camera of this embodiment will be described. FIG. 2 is a diagram showing a tracking curve obtained by fitting at the wide end and the tele end, and shows a design value curve ZT0 and an actual value curve ZT1 at an appropriate position showing an example of a product. When the change of the actual value is viewed based on the design value based on this figure, the tracking deviation curve as shown in FIG. 3 is obtained.

In FIG. 3, the horizontal axis X represents the relative zoom position coordinates, and the vertical axis Y represents the deviation amount indicating the difference from the design value line ZT0. Curve Z
The point indicating the maximum value d at which the amount of deviation between T1 and the design value curve ZT0 reaches a peak is designated. Let the zoom position at that time be the position C as an extreme value. Further, it can be regarded as a bowl-shaped diagram composed of the deviation amount tracking curves ZDw and ZDt on the left and right sides of the origin O. The zoom position C that gives the maximum value corresponds to the second information, and the maximum value d
Corresponds to the first information. The value of the difference in zoom position from the origin O to the wide end is Lw, and the value of the difference in zoom position from the origin O point to the tele end is Lt.

In the camera of the present embodiment, since the displacement amount curves ZDt and ZDw in FIG. 3 have the peak point at the origin O, they can be simply defined by the coefficient a or b, respectively. Approximate with the following curve formula: Y = a · X ² ‥‥‥‥‥‥‥‥‥‥‥‥‥ (1) or Y = b · X ² ‥‥‥‥‥‥‥‥‥‥‥‥‥ (2). The values of the coefficients a and b are given by the shift maximum value d, which is a unique value for each lens of each product, and stored in the memory 15. Then, it is read out as needed and used for calculation. However, this maximum value d does not change with respect to the subject distance as described above, because it does not change with respect to the subject distance. Of course, it may be treated as changing with respect to the subject distance. Further, the zoom position C that gives the maximum value d is a value that is unique to each lens, so it may be stored in the memory 15 for each lens, but since there is little variation in the value itself, this embodiment is the same. The same value is used for the lens of the model.

Now, the third position, which is indicated by the relative position of the origin O to which the zoom position at that time point and the zoom position C correspond,
The positional difference, which is information, is Xp. Further, the coordinates of an arbitrary point P on the displacement amount curves ZDw and ZDt at that position are represented by (X
p, Yp), the correction amount hp is a deviation amount from the design value in the position difference Xp and is a value to be corrected.
Is obtained as the difference between the value Yp obtained by substituting Xp for X in the quadratic equations (1) and (2) and the maximum deviation amount d (see FIG. 3). Further, the zoom position C indicating the maximum deviation and the zoom position difference to each wide or tele end are Lw and Lt, and the quadratic curve is the coordinate (L
w, d) or from coordinates (Lt, d),
The coefficients a and b in the equations (1) and (2) are d / (L
w ² ), d / (Lt ² ).

The above equations (1) and (2) are expressed by Yp = (d / Lw ² )) Xp ² ‥‥‥‥‥‥‥‥ (3) or Yp = (d / Lt ² ))・ Xp ² ‥‥‥‥‥‥‥‥‥‥‥‥ (4). Then, the correction amount hp is obtained from hp = d−Yp.

Further, the "deviation amount" of the tracking curve shown in FIGS. 2 and 3 shows the case where it is deviated in the plus direction with respect to the design value, but it may be deviated to the minus side as a matter of course. Also in that case, the above equations (3) and (4) can be applied with the value of d as a negative value.

The zoom tracking control operation of the camera of the present embodiment constructed as above will be described with reference to the flowcharts of FIGS. FIG. 4 is a flow chart of a subroutine "WT correction calculation" processing for obtaining a correction value hp which is the tracking deviation amount in the zoom tracking control of the present embodiment. First, step S
1, the maximum tracking deviation amount d from the design value at the corresponding subject distance is read from the memory 15. In step S2, the difference between the zoom position P and the zoom position C indicating the maximum displacement amount is obtained, and the value is calculated as the position difference Xp.
(See FIG. 3).

In step S3, the zoom position P
It is determined whether the zoom position C is the wide side or the tele side from the zoom position C that indicates the maximum displacement amount. That is, the sign of the value Xp is checked. In the case of positive (tele side), the process proceeds to step S4, and the value Yp is calculated from the equation (4). If the value is negative (on the wide side), the process proceeds to step S5, and the value Yp is calculated from the equation (3). Then, in step S6, the correction value hp corresponding to the shift amount is calculated by the above equation (5), and the present processing is ended. Note that the arithmetic processing from step S1 to step S6 described above is performed by the arithmetic means incorporated in the zoom tracking control block 7.

In the camera of this embodiment, the "WT
"Between correction calculation" is performed to obtain a correction value of the shift amount and zoom tracking control is performed. FIG. 5 is a flowchart of the subroutine "zoom tracking processing I" of the processing. First, in steps S <b> 21 and S <b> 22, the focus lens position and the zoom lens position in the initial tracking operation, which is the time point, are captured. Then, the process proceeds to step S23 and the subroutine "W" shown in FIG.
The correction value hp is obtained by calling "correction calculation between T". In step S24, a calculation reference value for zoom tracking at the zoom position and the focus position at that time is obtained. The calculation reference value is a reference value for obtaining a tracking curve by the table interpolation method, and corresponds to a constant ratio Da / Db of the feeding amount in the conventional example.

Then, in step S25, the next zoom lens position data is fetched, and in step S26, zoom tracking calculation is performed according to the calculation reference value.
In step S27, the “WT correction calculation” is executed again.
Subsequently, in step S28, the target focus lens position information is output based on the zoom tracking calculation result and the shift correction value, and the focus lens is driven,
In step S29, it is checked whether the output value of the zoom encoder 9 has been updated. If updated, the process returns to step S25, and if not updated, this routine ends.

The above-described series of tracking operations is performed in FIG.
In the following description, it is assumed that the current zoom lens position is at position X1 and the focus lens position is at the actual focus position Pa. Here, when the zooming instruction is input to the position X2, the position P on the zoom tracking curve (solid line) as the design value corresponding to the actual in-focus position Pa is calculated by the “WT correction calculation”.
Find b. Next, the focus lens position Pc with respect to the zoom position X2 is obtained along this zoom tracking curve (solid line). Further, the “WT correction calculation” at the zoom lens position X2 is performed to obtain the correction position Pd of the focus lens (the point at which focus can be actually obtained at the zoom lens position X2). Then, the focus lens is driven from the position Pa to the zoom tracking correction position Pd.

As described above, in the zoom tracking control in the camera of the present embodiment, it is possible to calculate the correction amount of the variation of the appropriate movement amount of the focus lens 4 during the zoom tracking in the manufacturing thereof. It is possible to suppress out-of-focus blur caused by zooming operation as much as possible.

Next, the zoom tracking control of the video camera of the present invention will be described in more detail. The configuration of the camera of this example is the same as the configuration of the camera of the first example of FIG. 1, except that a storage unit for the previous initial zoom lens position data is additionally provided in the memory 15, and an AF control block is provided. From 10 to the zoom tracking control block 7, A
The flag "A" indicating that the value becomes 1 when the F process is performed
The output of the "F FLG" signal is different. Further, the zoom tracking control block 7 further uses the flag "AF FLG" signal to determine whether or not the AF operation is performed between the previous zoom tracking operation and the current zoom tracking operation.
The operation progress recognition means is built in, and further, the comparison means for comparing the current value of the position of the zoom lens with a value before the current value is built in. Then, in the control block 7, it is assumed that a reference value in the interpolation calculation of the tracking curve is selected based on the result of the above-described operation progress recognition and comparison, and zoom tracking control is performed based on the reference value.

The zoom tracking control operation of the camera of this example will be described with reference to the flowchart of the subroutine "zoom tracking processing II" in FIG. First, in steps S31 and S32, focus lens position and zoom lens position information at the initial stage of the tracking operation are fetched.

Next, in step S33, it is checked whether or not the AF operation has been executed between the previous zoom tracking operation and the current zoom tracking operation.
This check is performed by referring to the flag "AF FLG", and the flag "AF FLG" is displayed when the AF operation is executed.
LG ”is set to 1. As a result of the check,
When the flag “AF FLG” is 1 and the AF operation has been performed, the process proceeds to steps S35 and S36.
Then, the subroutine "WT-to-WT correction calculation" processing shown in FIG. 4 is performed to obtain the correction value of the shift amount, and further, the reference value for zoom tracking is calculated, and the process proceeds to step S37.

On the other hand, if the flag "AF FLG" is 0 and the AF operation has not been performed, it means that the subject distance has not changed. Therefore, it is determined that the reference value setting need not be changed, and the process proceeds to step S34. It is checked whether the initial zoom position of this time is on the tele side of the previous initial zoom position. If it is on the tele side, the process proceeds to steps S35 and S36, and the subroutine "inter-WT correction calculation" is performed.
Processing is performed to calculate the reference value for zoom tracking, and the process proceeds to step S37. Even if it is not on the tele side, it is determined that it is not necessary to change the setting of the correction value or the reference value, and the process directly proceeds to step S37.

When it is determined in step S34 that the initial zoom position of this time is wider than the initial zoom position of the previous time, the WT correction calculation and the reference value calculation for zoom tracking are performed. The reason for not performing is to improve the accuracy of zoom tracking. That is, as shown in FIG. 11, the tracking curve interval is narrow on the wide side, and the tracking curve selection accuracy is relatively poor. Therefore, when zoom tracking is performed several times in a state where the subject distance does not change, the reference value is not calculated each time, but the reference value calculated on the tele side as much as possible by the above determination is used. By doing so, the accuracy of zoom tracking is improved.

In step S37, the next zoom lens position data is fetched, and in step S38, zoom tracking calculation is performed according to the calculation reference value. In step S39, "WT correction calculation" is executed. Subsequently, in step S40, the target focus lens position information is output based on the zoom tracking calculation result and the shift correction value, and the focus lens 4 is driven. Then, in step S41, it is checked whether the output value of the zoom encoder 9 has been updated. If it has been updated, the process returns to step S37. If it has not been updated, the flag "AF FLG" is reset to 0 in step S42, and this routine ends.

As described above, in the zoom tracking control of the camera of this example, the AF operation is not performed,
In other words, if the subject distance does not change and the initial zoom position during the previous zoom operation is on the tele side of the initial zoom position this time, it is possible to perform highly accurate tracking by using the previous reference value. Become.

In the camera of the present invention, the following constitution can be further adopted. That is, the configuration of the camera of this example is substantially the same as that of the above-described example, but the AF control block 10 of FIG.
Includes a predictive control means for performing tracking control based on the focus lens proper position predicted to be in focus.

In the case of this example, focusing is not completed A
As a process when zoom tracking needs to be performed during the F operation and a calculation reference value for zoom tracking is required, a focus position is predicted during the AF operation, and zoom tracking control is performed on the predicted focus position. To do. In the case of the present embodiment, a known MTF ratio AF method as disclosed in Japanese Patent Application Laid-Open No. 2-275916 is adopted as the method for predicting the in-focus position. However, the focus position prediction is not limited to this prediction method, and another focus prediction method may be adopted.

FIG. 7 is a subroutine "zoom tracking processing II" for zoom tracking control of the camera of this example.
It is the figure which showed the flowchart of "I". First, in step S51, it is determined whether or not the AF process is currently being performed. If the AF process is not currently in progress, the process proceeds to step S53, and the subroutine "zoom tracking process II" (step S31 and subsequent steps) in the camera of the above example is performed. ).

If AF processing is in progress, step S52.
Then, the AF control block 10 predicts the in-focus position by the AF prediction method, and sets the predicted position to the reference focus lens position. Then, the process proceeds to step S57. The processing after step S57 is the same as the "zoom tracking processing II" (processing after step S35) of the camera of the above example.

As described above, in the camera of this example, even if the zooming instruction is given during the AF operation, the focus position is immediately predicted, the focus lens position is set, and the zoom tracking control operation is started. It is possible. Therefore, even in such a state, there are no problems such as a delay in zoom operation and zooming in a state where the subject is out of focus.

Incidentally, the value applied as the calculation reference value for interpolating the zoom tracking position in each of the above-mentioned examples was the value Da / Db of the ratio of the extension amount of the focus lens (see FIG. 9). Not limited to this, for example, a camera previously proposed by the present applicant (1992 patent application No. 268877)
No.) zoom tracking control method, the ratio of the amount of repetition at the subject distance to the reference extension amount from the infinity tracking curve at the wide end and the tracking curve for the subject at the infinity The calculated value may be used as a calculation reference value in the method.

Further, although all of the above-mentioned embodiments are applied to the video camera, the present invention is not limited to this, and is also applied to the zoom tracking control of the still video camera and the silver halide film camera. It is possible to

[0042]

As described above, according to the present invention, the tracking curve selection, the lens position correction calculation, and the like can be performed with relatively high accuracy in the process of repeatedly performing the shooting operation (or the shooting preparation operation). In this case, the zoom tracking control, which is advantageous in terms of accuracy, can be performed on the basis of the recognition of the shooting operation history regarding these.

[Brief description of drawings]

FIG. 1 is a main block configuration diagram of a video camera according to an embodiment of the present invention.

2 is a diagram showing an example of a design value curve and a shift amount curve of zoom tracking applied to the zoom tracking processing of the video camera of FIG. 1;

FIG. 3 is a diagram showing an example of a shift correction curve for zoom tracking applied to zoom tracking processing of the video camera shown in FIG. 1;

FIG. 4 is a flowchart of a subroutine “inter-WT correction calculation” in the zoom tracking control of the video camera of FIG.

5 is a flowchart of a subroutine "zoom tracking processing I" in zoom tracking control of the video camera shown in FIG.

FIG. 6 is a subroutine “zoom tracking processing II” in zoom tracking control of the video camera of the present invention.
Flow chart.

FIG. 7 is a subroutine “zoom tracking processing II” in the zoom tracking control of the video camera of the present invention.
I "flow chart.

FIG. 8 is an example of a zoom tracking curve used for zoom tracking control of a conventional video camera.

FIG. 9 is a zoom tracking curve for explaining an interpolation calculation method of zoom tracking control of a conventional video camera.

FIG. 10 is a view showing a zoom tracking curve applied to zoom tracking control of a conventional video camera, showing a state of variation in an actual value with respect to a design value curve.

FIG. 11 is a diagram showing a zoom tracking curve used for zoom tracking control of the video camera, showing a state in which the curve spreads toward the tele end.

[Explanation of symbols]

2 zoom lens 4 focus lens 7 zoom tracking control block (maximum deviation information recognition means, zoom recognition means, correction value calculation means) (autofocus operation history recognition means, magnification comparison means, reference selection means) (zoom tracking control means, prediction Control means) 10 AF control block (autofocus means) (focus prediction means) 15 Memory (zoom tracking curve data holding means as a design value) C Zoom lens position (second information) showing the maximum value of the deviation amount Deviation Maximum value of amount (first information) Xp Difference between zoom lens position at that time point and zoom lens position indicating maximum value d (third information) Yp From the point showing the maximum value for obtaining the correction value of the deviation amount Zoom value change amount hp Offset value correction value

Claims (1)

[Claims] 1. A zoom tracking curve data possession that retains a plurality of zoom tracking curve data representing an appropriate position of the focusing lens for maintaining a focused state according to a change in magnification of the zoom lens under a constant subject distance. Means, an operation history recognizing means for recognizing a history of operations relating to the autofocus means from a time point before the present time to the present time, and a comparing means for comparing the current value of the magnification of the zoom lens with the immediately preceding value, Reference value of interpolation calculation for selecting the zoom tracking curve data to be applied according to the recognition by the operation history recognition means and the comparison result by the comparison means or for obtaining the proper position of the focusing lens along the zoom tracking curve data. Is equipped with a reference value selection means for selecting The camera to collect.