JP3387627B2 - camera - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera equipped with an inner focus type lens system.

[0002]

2. Description of the Related Art FIG. 5 shows a schematic configuration of a conventionally used inner focus type lens system.
In the figure, reference numeral 501 is a first fixed lens group fixed to a lens barrel (not shown), and 502 is a variably mounted lens movably mounted on the lens barrel (variable magnification lens (first lens group)). 1 lens group), 503 is a diaphragm for adjusting the amount of incident light from the first fixed lens group 501 and the variable power lens 502, 504 is a second fixed lens group fixed to the lens barrel, and 505 is the lens A focus competition lens (second lens group) movably attached to the lens barrel and having a so-called competition function for correcting the focus adjustment function and the movement of the focal plane due to zooming, 506 is a CCD
And the like. As is well known, in the lens system configured as shown in FIG.
Since 05 has both the competition function and the focus adjustment function, even if the focal lengths are the same, the position of the focus competition lens 505 for focusing on the imaging surface of the imaging element 506 varies depending on the subject distance.

When the object distance is changed at each focal length, the position of the focus compensating lens 505 for focusing on the image pickup surface of the image pickup device 506 is continuously plotted, as shown in FIG. FIG. 6 is a diagram showing the relationship between the focal length (variable magnification lens position) and the focus competition lens position. During zooming, if the trajectory shown in FIG. 6 is selected according to the subject distance and the focus compensating lens 505 is moved according to the trajectory, zooming without blurring is possible.

On the other hand, in the front-lens focus type lens system, an independent focus compensating lens is provided for the variable power lens, and the variable power lens and the focus compensating lens are connected by a mechanical cam ring. There is.
Therefore, for example, if a knob for manual (manual) zoom is provided on this cam ring and the focal length is manually changed, no matter how fast the knob is moved, the cam ring will follow this and rotate and change. Since the double lens and the focus competition lens move along the cam groove of the cam ring, if the focus competition lens is in focus, the above operation does not cause blurring.

In controlling the inner focus type lens system having the above-mentioned characteristics, a plurality of pieces of locus information shown in FIG. 6 are used in some form for a lens control microcomputer (hereinafter referred to as a lens control microcomputer). In general, a locus is selected according to the positions of the focus compensating lens and the variable power lens, and zooming is performed while following the selected locus.

Further, in order to read the focus competition lens position with respect to the zoom lens position from the storage element and apply it for lens control, it is necessary to read each lens position with a certain degree of accuracy. In particular, as is clear from FIG. 6, when the variable power lens moves at a constant speed or a speed close to it, the inclination of the trajectory of the focus competition lens changes every moment due to the change in the focal length. This indicates that the moving speed and moving direction of the focus compensating lens change every moment, in other words, the actuator of the focus compensating lens is 1 Hz to several hundreds of H.
It is necessary to make an accurate speed response up to z.

It is becoming more common to use a stepping motor for the focus compensating lens of the inner focus lens system as an actuator that satisfies the above requirements. The stepping motor rotates in perfect synchronization with the step pulse output from the lens control microcomputer, etc., and the step angle per pulse is constant, so high speed response, stop accuracy, and position accuracy can be obtained. Is possible. Furthermore, when a stepping motor is used, since the rotation angle with respect to the step pulse number is constant, the step pulse can be used as it is as an increment type encoder, and it is not necessary to add a special position encoder. is there.

As described above, when an attempt is made to perform a zooming operation while keeping the focus by using the stepping motor,
The locus information as shown in FIG. 6 is stored in a lens control microcomputer or the like in some form (the locus itself may be a function having the lens position as a variable), and the locus may be changed according to the position or the moving speed of the variable power lens. It is necessary to read information and move the focus compensating lens based on the information.

FIG. 7 is a diagram for explaining an example of a conventionally known trajectory following method. In FIG. 7A, the vertical axis represents the focus competition lens position, and the horizontal axis represents the variable power lens position. In addition, FIG.
Middle, a0, a1, a2 ,. ． ． a6 and b0, b1, b
2 ,. ． ． b6 is a representative locus stored in the lens control microcomputer. The lens control microcomputer is
Information on the cam locus is stored in the table data shown in FIG. FIG. 7B is a diagram showing focusing focus compensating lens position data A (n, v) that varies depending on the object distance depending on the zoom lens position. As is apparent from FIG. Direction, and the variable power lens position (focal position) changes in the row direction of the variable v. For example, n = 0 represents the subject distance at infinity, the subject distance changes to the closest distance as the variable n increases, and n =
m indicates the closest subject distance. On the other hand, v = 0 represents the wide end, the focal length increases as the variable v increases, and v = s represents the zoom lens position at the tele end.
Therefore, one cam locus is drawn with one row of table data. In addition, in FIG. 7B, p0, p1, p
2 ,. ． ． p6 is a locus calculated based on the above two loci. This locus is calculated by the following equation (1).

P (n + 1) = | p (n) -a (n) | /
| B (n) -a (n) | × | b (n + 1) -a (n +
1) | + a (n + 1) (1) According to the formula (1), for example, in FIG. 7, when the focus compensating lens is at the position p0, p0 is the line segment b0.
The ratio that internally divides -a0 is obtained, and the line segment b1-
The point that internally divides a1 is p1. From the position difference between p1 and p0 and the time required for the variable power lens to move from Z0 to Z1, the moving speed of the focus compensating lens for maintaining focus can be known.

Next, a case will be described in which the stop position of the variable power lens is not limited only to the boundary where the stored representative trajectory data is owned. FIG. 8 is a diagram for explaining an interpolation method in the position of the variable power lens.
A part of (a) is extracted and the zoom lens position is arbitrarily set.

In FIG. 8, the vertical axis represents the focus competition lens position, and the horizontal axis represents the variable power lens position. The representative locus position (focus lens position relative to the variable power lens position) stored in the lens control microcomputer is shown. ,
Variable magnification lens position “Z0, Z1, ... Zk−1, Z
k. ． ． Zn ”, and the focus lens position at that time is represented by“ a0, a1 ,.
k. ． ． an "and" b0, b1, ... bk-1, b
k. ． ． bn ”.

Now, when the zoom lens position is not on the zoom boundary and is zx and the focus competition lens position is px, the focus competition lens positions ax and bx are obtained by the following equations (2) and (3). You can

Ax = ak- (Zk-Zx) * (ak-a)
k-1) / (Zk-Zk-1) ... (2) bx = bk- (Zk-Zx) * (bk-bk-1) /
(Zk−Zk−1) (3) In other words, according to the internal division ratio obtained from the current zoom lens position and two zoom boundary positions (for example, Zk and Zk−1 in FIG. 8) that sandwich the zoom lens, the memory is stored. 4 representative trajectory data (ak, ak-1, bk, bk- in FIG. 8)
By internally dividing the one having the same subject distance in 1) by the internal division ratio, the focus compensating lens position ax,
Each bx can be calculated. Then, according to the internal division ratio obtained from the focus compensating lens positions ax, px, bx, the same focal length among the four representative data stored (ak, ak-1, bk, bk-1 in FIG. 8). Of the following tracking focus compensating lens position p
It is possible to obtain k and pk-1. Then, when zooming from wide to tele, the focus is maintained from the positional difference between the follow-up focus compensating lens position pk and the current focus compensating lens position px, and the time required for the zoom lens to move from Zx to Zk. You can see the moving speed of the focus compensating lens. Also, when zooming from tele to wide, the position difference between the follow-up focus compensating lens position pk-1 and the current focus compensating lens position px and the time required for the zoom lens to move from Zx to Zk-1 are combined. You can see the moving speed of the focus compensating lens to keep the focus. The above-mentioned trajectory tracking method has been conventionally devised.

When the variable power lens moves from the telephoto to the wide direction, as is apparent from FIG. 6, the scattered locus is in the direction of convergence, so that the in-focus state can be maintained even by the above-mentioned locus tracking method. However, when the variable power lens moves from the wide-angle direction to the tele direction, it is not known which path the focus compensating lens at the convergence point should follow. I can't keep up.

FIG. 9 is a diagram for explaining an example of a trajectory following method conventionally devised to solve the above problem.

In both (a) and (b) of the figure, the horizontal axis represents the position of the variable magnification lens, and the vertical axis of (a) represents the level of the high frequency component (sharpness signal) of the video signal which is the AF evaluation signal. And the vertical axis in (b) indicates the focus compensating lens position. In FIG. 9, it is assumed that the focus cam locus is 604 when zooming is performed on a certain subject.
Here, the zoom position 606 (Z14) in FIG. 9B
The focusing cam trajectory following speed on the wider side is positive (moved in the direction closest to the focus compensating lens), and the zoom position is 6 as well.
The following speed of the focusing cam locus that moves in the infinite direction on the telephoto side from 06 is negative. When the focus competition lens follows the cam locus 604 while maintaining the in-focus state, the magnitude of the sharpness signal becomes like the maximum value level 601 in FIG. 9A. In general, it is known that the sharpness signal level has a substantially constant value in zooming while maintaining the in-focus state.

In FIG. 9B, the moving speed of the focus compensating lens tracing the focusing cam locus 604 during zooming is Vf0. When the actual moving speed of the focus compensating lens is Vf, and the zooming is performed while changing the magnitude with respect to the moving speed Vf0 of the focus compensating lens tracing the cam locus 604, the locus becomes a zigzag locus like 605. At this time, the sharpness signal level changes so as to generate peaks and valleys as shown by a locus 602. Here, the size of the locus 603 in FIG. 9A becomes maximum at the position where the loci 604 and 605 intersect (the even points of Z0, Z1, ... Z16),
Z0, Z at which the moving direction vector of the locus 605 switches
1 ,. ． ． The level of the locus 603 becomes the minimum at an odd point of Z16. The sharpness signal level 602 in FIG. 9A is the minimum value of the locus 603, but conversely, the level TH1 of the sharpness signal level 602 is set, and the locus 605 is set every time the size of the locus 603 becomes equal to TH1. When the moving direction vector of is switched, the moving direction of the focus compensating lens after the switching can be set to a direction approaching the focus locus 604. That is, the sharpness signal levels 601 and 60
By controlling the moving direction and moving speed of the focus compensating lens so as to reduce the blur amount each time the image blurs by a difference of 2 (TH1), zooming with the blur amount suppressed can be performed.

By using the above-described method, in zooming from wide to tele, where the cam locus as shown in FIG. 6 diverges from the convergence, even if the focusing speed Vf0 is not known, based on FIG. In response to the following speed (calculated using p (n + 1) obtained from the equation (1)) described above, the switching operation is performed as shown by a locus 605 in FIG. 9B while controlling the moving speed Vf of the focus compensating lens. By repeating the above (according to the change in the sharpness signal level), it is possible to select a locus in which the sharpness signal level does not drop below 602 (TH1), that is, the blurring of a certain amount or more does not occur. Further, by appropriately setting the level TH1 of the sharpness signal level 602 as the magnitude of the blur amount, it is possible to perform zooming in which the blur is visually unnoticeable.

Here, the moving speed Vf of the focus compensating lens is expressed by the following equations (4) and (5), where (Vf +) is the correction speed in the positive direction and (Vf-) is the correction speed in the negative direction. Decided.

Vf = Vf0 + (Vf +) (4) Vf = Vf0 + (Vf-) (5) At this time, the correction speeds (Vf +) and (Vf-) are the ones when the following locus is selected by the zooming method. In order to prevent the deviation, the interior angle of the two direction vectors of the moving speed Vf of the focus compensating lens obtained by the equations (4) and (5) is determined so as to be bisected by the direction vector of Vf0. It Furthermore, when the sharpness signal is increased or decreased during the zooming operation where the focus point is unknown, the cam locus of the point showing the maximum value of the sharpness signal is specified as the focusing cam locus,
By determining the standard moving speed Vf0 of the focus competition lens from the cam locus, superimposing the correction speeds (Vf +) and (Vf-) on the standard moving speed Vf0, and zooming while updating the focusing cam locus. , The focus following ability during zooming is improved.

On the other hand, during the non-variable magnification operation, focus adjustment (autofocus) is automatically performed by moving the focus compensating lens so that the sharpness signal becomes maximum. Therefore, considering that the focus competition lens moves due to autofocus in response to changes in subject distance,
During non-variable magnification operation, the focus cam locus is always updated according to the lens position at that time.

[0023]

However, in the above-mentioned conventional example, since the focusing cam locus is always specified from the current lens position at the end of zooming, there are the following drawbacks.

When the zoom is ended at a position where the focus lens is not on the in-focus cam locus, the in-focus cam locus is erroneously specified as the in-focus cam locus. After that, when the zooming is started again, the standard moving speed Vf0 of the focus compensating lens is obtained based on the incorrectly identified focusing cam locus, so that the focusing cam locus cannot be traced during zooming and there is a drawback that a blur is visible. .

This will be described with reference to FIG. In the figure, reference numeral 1001 is a focusing cam locus, 1002 is a zoom start position, 1003 is a position which intersects the focusing cam locus during zooming, and 1004 is a zoom end position. Now, it is assumed that zooming is performed from the zoom start position 1002 to the zoom end position 1004. During zooming, the sharpness signal becomes maximum because it intersects with the focusing cam locus at a position 1003 where it intersects with the focusing cam locus. Therefore, 1001 can be specified as the focus cam locus. However, zoom end position 1
When the zoom is finished at 004, the cam locus 1005 is not the actual focusing cam locus, but the current focus compensating lens positions 1004 to 1005 are erroneously specified as the focusing cam locus. If the zoom is restarted in this state, the tracking target position pn + 1 in the formula (1) is set to 10
Therefore, the standard moving speed Vf0 of the focus compensating lens becomes the speed vector 1007, and the original focusing cam locus 1001 cannot be traced.

On the other hand, if the focus locus is not updated after zooming, the focus compensating lens is moved by autofocus in response to the change in the object distance, and the focus cam is changed even if the actual focus cam locus is changed. The locus is not updated, and when zooming is performed thereafter, zooming is performed at the standard moving speed Vf0 of the focus compensating lens obtained based on an incorrect focusing cam locus different from the actual focusing cam locus. The focus cam locus cannot be traced and blurring occurs.

The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain a blurring within a predetermined time even if the zooming is performed again after the zooming operation is finished except on the focus cam locus. It is an object of the present invention to provide a camera that does not cause blurring and does not cause blurring even when zooming is performed after the focus compensating lens is moved by autofocus.

[0028]

In order to achieve the above object, a camera of the present invention comprises a first lens group that performs a zooming operation, and a first lens group that corrects the movement of a focal plane when the first lens group moves. A camera that performs a zoom operation by two lens groups and a lens group driving unit that moves the first and second lens groups independently of each other in parallel with the optical axis .
Extraction means for extracting a predetermined focus signal that changes according to the focus state from the image signal of the subject for automatic focus adjustment by the lens group, and the focus position of the second lens group with respect to the position of the first lens group. Recording means for recording information according to the subject distance, calculating the subject distance based on the positions of the first and second lens groups and the focus position information recorded in the recording means, and specifying the subject distance And a standard moving speed of the second lens group for correcting the movement of the focal plane with respect to the movement of the first lens group, according to the subject distance calculating means and the subject distance specified by the subject distance calculating means. A moving speed calculating means and a speed correcting hand for correcting the standard moving speed of the second lens group calculated by the moving speed calculating means so that the level of the focus signal increases or decreases during the zooming operation. If, zooming operation is completed after a predetermined time, the
Autofocus based on the focus signal extracted by the extraction means
The second lens that changes when an adjusting operation is performed.
It is characterized in that it has a said prohibit manual stage to prohibit specific subject distance by the object distance calculating means with respect to the position of the group's.

[0029]

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram showing the structure of a camera according to an embodiment of the present invention. In FIG.
Is a first fixed (front lens) lens group fixed to a lens barrel (not shown), and 102 is movably attached to the lens barrel and is a zoom lens (first lens) for zooming.
(Lens group), 103 is an aperture for adjusting the amount of incident light from the first fixed lens group 101 and the variable power lens 102, and 104 is a second fixed lens group fixed to the lens barrel.
Reference numeral 5 denotes a focus competition lens (second lens group) that is movable with respect to the lens barrel and has both a competition function and a focusing function. These first fixed lens group 101, variable power lens 102, diaphragm 103, By the second fixed lens group 104 and the focus competition lens 105,
An inner focus type lens system is configured. An image pickup element 106 such as a CCD has an image pickup surface on which the image light transmitted through the lens system is formed, and converts the image light into an image signal by photoelectric conversion.

A first amplifier 107 amplifies the output signal from the image pickup element 106 to a specified level. 1
Reference numeral 08 denotes a camera signal processing circuit, which performs a predetermined process on the output signal from the amplifier 107. A second amplifier 109 amplifies the video signal processed by the camera signal processing circuit to a specified level. 110 is an LCD
The display circuit performs a predetermined process on the output signal from the second amplifier 109 in order to display the output signal on the display means. An LCD (Liquid Crystal Display) 111 is a display unit for displaying a captured image.

On the other hand, the video signal amplified at 107 is sent to the aperture control circuit 112 and the AF (autofocus) evaluation value processing circuit 114, respectively. Aperture control circuit 112
Then, depending on the video signal input level, the IG driver 11
3 and the IG meter 114 are driven to control the diaphragm 103 to adjust the light amount. AF evaluation value processing circuit 11
In No. 4, only the high frequency component of the video signal in the distance measurement frame is extracted and processed according to the gate signal from the distance measurement frame generation circuit 116. Reference numeral 115 denotes an AF microcomputer (hereinafter, referred to as AF microcomputer), which is a distance measuring frame for controlling the drive of the variable magnification lens 102 and the focus compensating lens 105 and changing the distance measuring area according to the strength of the AF evaluation signal. It is in control. Further, the AF microcomputer 115 communicates with a system control microcomputer (hereinafter, referred to as syscon) 124,
A zoom switch unit 125 that is read by the system controller 124 through A / D conversion or the like (a unitized zoom switch outputs a voltage according to the rotation angle of the operating member. Variable speed zooming is performed according to this output voltage. )
Information, zooming information under zoom controlled by the AF microcomputer 115, zooming operation information such as focal length, and the like are exchanged with each other.

Reference numeral 117 denotes a zoom driver, and 119 denotes an AF driver. The zoom driver 117 and the AF driver 119 respectively output from the AF microcomputer 115, the variable magnification lens 102 and the focus competition lens 105.
The driving energy is output to the lens driving motor in accordance with the driving command. 118 is a zoom motor, 12
Reference numeral 0 denotes a focus motor, and the zoom motor 118 and the focus motor 120 are respectively the zoom lens 10
2 and the focus competition lens 105 are driven.

Next, the zoom motor 118 for driving the lens
Also, assuming that the focus motor 120 is a stepping motor, a method of driving the motor will be described.

The AF microcomputer 115 determines the driving speed of the zoom motor 118 and the focus motor 120 by the program processing, and drives the zoom driver 117 and the focus motor 120 which drive the zoom motor 118 as the rotation frequency signal of each stepping motor. It is sent to each focus driver 119. Further, the drive / stop command of the zoom motor 118 and the focus motor 120 and the rotation direction command of the motors 118 and 120 are sent to the drivers 117 and 119. The drive / stop signal and the rotation direction signal of the zoom motor 118 depend mainly on the state of the zoom switch unit 125.
The focus motor 120 responds to a drive command determined by processing in the AF microcomputer 115 during AF and zoom.

Each of the drivers 117 and 119 sets the phases of the four motor excitation phases to forward and reverse rotation phases according to the rotation direction signal, and four motor excitation phases according to the received rotation frequency signal. By outputting while changing the applied voltage (or current) of each motor 118, 1
While controlling the rotation direction and rotation frequency of 20, the output to each of the motors 118 and 120 is turned on (ON) / off (OFF) in response to a drive / stop command.

FIG. 2 is a flow chart showing the control operation of the camera of this embodiment, which is processed in the AF microcomputer 115. In the figure, step S201 indicates the start of processing. Step S202 is an initialization routine, which processes the RAM and various ports in the AF microcomputer 115. Step S203 is an intercommunication routine with the system controller 124, in which information about the zoom switch unit 125 and zooming operation information such as the position of the zooming lens 102 are exchanged. Step S204 is A
This is a routine for processing the sharpness signal of the AF evaluation signal by the signal obtained from the F evaluation value processing circuit 114.

Step S205 is an AF processing routine.
Automatic focus adjustment processing is performed according to changes in the AF evaluation signal. Step S206 is a zoom processing routine,
6 is a processing routine of a competition operation for maintaining the in-focus state at the time of zooming operation, and in this routine, the focus competition lens 10 tracing the cam locus as shown in FIG.
The driving direction, the driving speed, and the like of No. 5 are calculated (the calculation method will be described later in detail with reference to FIG. 3).

In step S207, which one of the zoom and focus driving directions and driving speeds calculated in steps S205 and S206 is used is selected according to the AF mode and the zooming operation. However, it is a routine that is set so that it will not drive to the tele side from the tele end, the wide side from the wide end, the close side from the close end, and the infinite side from the infinite end, which is provided so that it does not hit the mechanical end of the lens. Is. In step S208, the drivers 117 and 1 are driven according to the driving direction information and driving speed information for zooming and focusing determined in step S207.
A control signal is output to 19 to control driving / stopping of the lens. After the processing of step S208 is completed, the above-mentioned step S2
Return to 03. The series of processes in FIG. 2 are executed in synchronization with the vertical synchronization period (waiting for the next vertical synchronization signal in the process of step S203).

FIG. 3 is a flow chart for explaining the details of the processing executed in step S206 of FIG. In the figure, step S301 is processing for initializing various parameters.
Zoom switch unit 12 obtained by communication with
The drive speed of the zoom motor 118 is set based on the information of No. 5, and the reversal flag indicating that the zigzag switching operation at the time of zooming from wide to tele described in the conventional example is performed is set to 0. In step S302, it is determined whether or not zooming is in progress. If zooming is not in progress, step S303 is performed.
Then, after zooming, the timer determines whether or not a predetermined time has elapsed. If the predetermined time has not elapsed, the post-zoom timer is added in step S304, and this processing ends. If a predetermined time has elapsed, the sharpness signal at this time is set to the peak value PK of the sharpness signal in step S305, and the variable power lens 10 at that time is set.
2 position and the position of the focus competition lens 105,
The focus cam locus is set from the stored representative cam table. The focusing cam locus indicates where on the representative cam table the variable magnification lens 102 and the focus compensating lens 105 exist at the time of focusing, and FIG.
When the focal point is P0, the ratio of P0 internally dividing the line segment b0-a0 (β) is P0-a0 / b0-a0 = α / β, and in FIG. 7 (b), a0 = A ( 0,0), b0 =
Since A (1,0), it becomes a point that α / β between n = 0 and 1 at v = 0, and that point is changed from wide to tele (v = 0,1,
..., s) is a locus. Therefore, the position of the variable power lens 102 and the focus competition lens 1 at that time
The focus cam locus can be set by calculating n, α, and β from the position 05.

If zooming is being performed in step S302, the timer is cleared after zooming in step S306.
The process moves to step S307. In step S307, it is determined whether the sharpness signal is larger than the peak value. If so, the sharpness signal is set to a peak value in step S308, and n, α, and β are obtained from the position of the variable power lens 102 and the position of the focus compensating lens 105 at that time, and the focusing cam locus is set. And step S3
At 09, a value obtained by subtracting an arbitrary value S from the sharpness signal at that time is set to TH1, and this corresponds to the level of 602 in FIG. 9A. Then, the process proceeds to step S311. If the sharpness signal is smaller than the peak value in step S307, the focus cam locus (n,
Substitute α, β) into the standard cam locus (n ′, α ′, β ′). In the series of operations from step S307 to step S310, the sharpness signal 603 is the minimum value 60 in FIG.
From 2 to the maximum value 601, the focus cam locus (n,
α, β) is calculated, and the maximum value of the sharpness signal, which is the true focusing point passing through the maximum value 601, is set as the true focusing cam locus, and is set as the standard cam locus important for the focus following operation during zooming. is there.

In step S311, the follow-up target position pn + 1 obtained from the above equation (1) is calculated from the standard cam locus (n ', α', β ') and the locus data stored in the AF microcomputer 115. Using this, the standard (moving) speed Vf0 of the focus competition lens 105 is calculated. When the position of the variable power lens 102 is a position that does not have the stored data of the cam locus, the above-mentioned (2),
The follow-up target position is calculated from the equations (3) and (1). In step S312, the correction speeds (Vf +), (Vf
This is a process of calculating −). Here, the correction speed (Vf
+) And (Vf-) are calculated as follows.

FIG. 4 is a diagram for explaining a method of calculating the correction speeds (Vf +) and (Vf-). The horizontal axis of the figure shows the variable magnification lens position and the vertical axis shows the focus competition lens position, and it is assumed that 604 in FIG. 9B is a cam locus to be followed. Now, when the zoom lens position changes by x, the focus speed at which the focus competition lens position changes by y is the standard moving speed Vf0 (903 in FIG. 4) calculated in step S311 of FIG. When the lens position changes by x, the focus speed at which the focus competition lens position changes by n or m with reference to the displacement amount y is the desired correction speed (Vf
+) And (Vf-). Here, in FIG. 4, the speed at which the displacement amount y is driven closer to the side (standard movement speed Vf
0 and a correction speed (Vf +) in the positive direction are added), and a speed to drive infinitely from the displacement y (standard movement speed Vf0 and correction speed (Vf-) in the negative direction are added)
N and m are determined so that the direction vector 902 and the direction vector 902 have a direction vector 903 that is separated from the direction vector 903 of the standard moving speed Vf0 by an angle γ.

First, m and n are obtained. Graphically from FIG. 4, tan θ = y / x, tan (θ−γ) = (ym−x) / tan (θ + γ) = (y + n) / x (6) Further, tan (θ ± γ) = (Tan θ · tan γ) / (1 ± tan θ · tan γ) (7) From the above formulas (2) and (3), m = (x2 + y2) / (x / k + y) (8) n = (x2 + y2) / ( x / ky) (9) However, tan γ = k, and n and m are separated. here,
The size of the correction angle γ is 0.8 times in the middle range and 2 in the tele range, based on the value on the wide side depending on the focal length.
Change to double. By doing so, the increase / decrease cycle of the sharpness signal level that changes according to the drive state of the focus competition lens 105 can be kept constant with respect to the predetermined position change amount of the focus competition lens 105, and during zooming. , It is possible to reduce the possibility of missing the trajectory to be followed.

The values of k are stored as a table in the memory of the AF microcomputer 115 in accordance with the value of γ, and the values are read out as needed to calculate the equations (8) and (9).

Here, if the position of the variable power lens 102 changes by x per unit time, the zoom moving speed of the variable power lens 102 = x, the standard moving speed Vf0 = y of the focus compensating lens 105, and the correction speed (Vf +). ) = N,
(Vf −) = m, and according to the above equations (8) and (9),
Correction speeds (Vf +) and (Vf-) are obtained.

Returning to FIG. 3, in step S313, it is determined whether the zoom direction is from wide to tele.
If the determination result is negative (NO), in step S314 (V
With f +) = 0 and (Vf-) = 0, the processes from step S317 are performed. If the determination result of step S313 is affirmative (YES), it is determined in step S315 whether the current sharpness signal level is TH1 or less. If the determination result is negative (NO), the process proceeds to step S317, and if affirmative (YES), the step S31.
In step 6, the inversion flag is set to 1.

In step S317, it is determined whether or not the reversal flag = 1, and if the determination result is affirmative (YES), it is determined in step S318 whether or not the correction flag is 1. Here, the correction flag is a flag that indicates whether the cam locus following state is a state in which the correction in the positive direction is applied (correction flag = 1) or a correction state in the negative direction (correction flag = 0). If the determination result in step S318 is negative (NO), the correction flag = 1 (correction state in the positive direction) is set in step S321, and the focus compensating lens 105 is calculated by the above equation (4).
The moving speed of Vf = Vf0 + (Vf +). However,
(Vf +) ≧ 0 If the determination result in step S318 is affirmative (YES), the correction flag is set to 0 (correction state in the negative direction) in step S320, and the moving speed Vf of the focus compensating lens 105 is calculated from the above equation (5). Vf0 + (Vf-) However,
(Vf−) ≦ 0.

If the decision result in the step S317 is negative (NO), the step S319 is followed by the step S3.
Similar to step 18, it is determined whether or not the correction flag = 1, and if the determination result is affirmative (YES), the process proceeds to step S321, and if negative (NO), the process proceeds to step S320. Step S3
In step 22, the step S320 or the step S321 is performed.
Moving speed Vf of the focus competition lens 105 obtained in
Depending on whether is positive or negative, the focus drive directions are set to the close-up direction and the infinite direction, respectively, and this processing is exited.

With the above operation, the zoom processing operation of step S206 in FIG. 2 is completed, and thereafter, the motor is actually driven in steps S207 and S208.

A detailed description will be given with reference to FIG.
As described above, when zooming is performed from the zoom start position 1002 to the zoom end position 1004, the sharpness signal becomes maximum at a position 1003 that intersects with the focusing cam locus during zooming, and 1001 is specified as the focusing cam locus. And
When the zoom is finished at the zoom end position 1004, if the focus cam locus is not updated after the zoom is finished for a predetermined time, the follow-up target position pn + 1 in the above formula (1) becomes 1008 even if the zoom operation is performed again during that period. , The standard moving speed Vf0 of the focus competition lens 105 is the speed vector 10
As a result, the original focus locus 1001 can be traced.

In this way, by not updating the focus cam locus for a predetermined time after the zoom operation is completed, even if the zoom operation is performed again after the zoom operation is finished except on the focus cam locus, the zoom is performed within the predetermined time. If so, blurring due to the inability to follow the focus cam locus will no longer occur.

On the other hand, since the focusing locus is updated after a lapse of a predetermined time after the end of zooming, if the focus compensating lens 105 is moved by autofocusing in response to a change in the object distance, the focusing compensating lens 105 is adjusted according to the position of the focus compensating lens 105. Since the focus cam locus is updated, blurring due to the inability to follow the focus cam locus does not occur even if zooming is performed thereafter.

[0055]

As described above in detail, according to the camera of the present invention, after the zooming operation is completed, the focusing cam locus is not updated for a predetermined time, so that after the zooming operation is finished except on the focusing cam locus. Even if zooming is performed again, blurring due to the inability to follow the focus cam locus within a predetermined time will not occur. On the other hand, the focus locus is updated after a lapse of a predetermined time after zooming, so if the focus compensating lens moves by autofocus in response to changes in the subject distance, the focusing cam locus is updated according to the position of the focus compensating lens. Therefore, even if zooming is performed thereafter, blurring due to the inability to follow the focus cam locus does not occur.

Further, according to the present invention, in a camera of a type in which a focus signal is extracted from a video signal by an appropriate zoom operation, it is possible to simultaneously solve the problem of deterioration of focus detection accuracy due to blur due to zoom. There is also an effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a camera according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a control operation of the camera.

FIG. 3 is a flowchart for explaining in detail the processing contents in step S206 of FIG.

FIG. 4 is a diagram for explaining a method of calculating correction speeds (Vf +) and (Vf−).

FIG. 5 is a diagram showing a schematic configuration of a conventional inner focus type lens system.

FIG. 6 is a diagram showing a relationship between a variable power lens position and a focus competition lens position in the same lens system.

FIG. 7 is a diagram showing an example of a conventional trajectory following method.

FIG. 8 is a diagram for explaining an interpolation method in a variable power lens position direction.

FIG. 9 is a diagram showing an example of a conventional trajectory following method different from that of FIG. 7.

FIG. 10 is a diagram for explaining blurring.

[Explanation of symbols]

102 variable magnification lens (first lens group) 105 focus compensating lens (second lens group) 114 AF evaluation value processing circuit (high frequency component extraction means) 115 AF microcomputer (subject distance calculation means, standard movement speed calculation means, speed superposition means) , Recording means, prohibiting means, control means) 117 zoom driver (lens group driving means) 118 zoom motor (lens group driving means) 119 focus driver (lens group driving means) 120 focus motor (lens group driving means)

Claims (6)

(57) [Claims] And 1. A first lens group for performing zooming operation, the first
Second for correcting the movement of the focal plane when the lens group moves
Lens group and the first and the drawing by a lens group driving means for parallel movement and the optical axis of the second lens group independently
In the camera that performs the arm movement, the second lens group
Extraction means for extracting a predetermined focus signal that changes according to the focus state from the image signal of the subject for more automatic focus adjustment, and focus position information of the second lens group with respect to the position of the first lens group Recording means for recording according to the subject distance, subject for calculating the subject distance based on the positions of the first and second lens groups and the focus position information recorded in the recording means, and specifying the subject distance Distance calculating means, and a moving speed for calculating a standard moving speed of the second lens group for correcting the movement of the focal plane with respect to the movement of the first lens group according to the object distance specified by the object distance calculating means. a calculation unit, a speed correction means for correcting the standard traveling speed of the calculated by the moving speed calculating means and the second lens group so that the level at the time of the focus signal power variation operation is increased or decreased, zooming Work after the end of a predetermined time, said extraction means
Based on the focus signal extracted by the
Position of the second lens group that changes by being performed
Camera; and a said prohibit manual stage to prohibit specific subject distance by the object distance calculating means for. 2. The camera according to claim 1, wherein the first lens group is a variable power lens. 3. The camera according to claim 1, wherein the second lens group is a focus compensating lens. 4. The camera according to claim 1, wherein the lens group driving means includes a stepping motor. 5. The camera according to claim 1, wherein the extraction means is a circuit that extracts a high frequency component from the video signal to obtain an autofocus evaluation value. 6. The camera according to claim 1, wherein the speed correction unit corrects the speed of the second lens group by superimposing a correction speed on the standard speed.