JPH095604A - Lens control device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a lens control device capable of maintaining focus during zooming even when the focus position is not within the stored cam locus. is there. A variable power lens 102 and a focus lens 105 for correcting movement of a focal plane when the variable power lens is moved.
And an AF microcomputer 11 that stores the focus position of the focus lens with respect to the position of the zoom lens group according to the subject distance.
The moving speed of the focus lens that corrects the focal plane when moving the variable magnification lens is obtained from the memory in 6 and the cam locus stored in the memory, and the focus lens is stored in the memory and out of the focusable moving range. If the in-focus position of the focus lens exists in the position A, the moving speed of the focus lens for correcting the focal plane when moving the zoom lens is calculated based on the cam locus stored in the memory A.
A lens control device including an F microcomputer 116.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art FIG. 2 shows a simple structure of an inner focus type lens system.

In FIG. 2, 101 is a fixed first
Lens group 102, a second lens group (hereinafter referred to as a variable power lens) 102 that performs zooming, a diaphragm 103, a third lens group 104 that is fixed, and a focus adjustment function and a focus by zooming. A fourth lens group (hereinafter referred to as a focus lens) having a so-called competition function for correcting the movement of the surface, 106 is an image pickup element, and 106a is an image pickup surface.

As is well known, in the inner focus type lens system configured as shown in FIG. 2, since the focus lens 105 has both a compensator function and a focus adjustment function, even if the focal lengths are the same, the image pickup surface 1 is not affected.
The position of the focus lens 105 for focusing on 06a varies depending on the subject distance.

Even if the subject distances are the same, if the focal length changes due to the zooming operation, the focus lens position for focusing becomes different.

When the position of the focus lens 105 for focusing on the image pickup surface is continuously plotted while the variable power lens is being driven to perform the variable power operation for each object distance, FIG. become that way.

In FIG. 3, the abscissa axis represents the zoom lens position, that is, the focal length, and the ordinate axis represents the focus lens position, that is, the subject distance.

During the zooming operation, if one of the loci shown in FIG. 3 is selected according to the object distance and the focus lens 105 is moved according to the locus,
This allows variable magnification operation without blur.

Incidentally, in the front lens focus type lens system, an independent compensator lens is provided for the variable power lens, and the variable power lens and the compensator lens are connected by a mechanical cam ring.

Therefore, for example, when a knob for 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 to change the magnification. Since the lens and the competing lens move along the cam groove of the cam ring, if the focus lens is in focus, the above operation does not cause blurring.

However, in the control of the inner focus type lens system having the above-mentioned features, the plurality of locus information shown in FIG. 3 is stored in the lens control microcomputer in some form and changed from the focus lens. In general, a locus is selected and specified according to the position of the double lens, and zooming is performed while tracing the selected locus.

Further, since the position of the focus lens with respect to the position of the variable power lens is read from the memory in the microcomputer for lens control and is applied for lens control, the position of each lens is not read with a certain degree of accuracy. must not.

As is clear from FIG. 3, in particular, when the variable power lens moves at a constant speed or a speed close to it, the inclination of the locus of the focus lens changes every moment due to the change of the focal length.

This indicates that the moving speed and the moving direction of the focus lens change every moment, in other words, the actuator of the focus lens must make an accurate speed response from 1 Hz to several hundreds Hz. It will not happen.

As an actuator that satisfies the above requirements, it is becoming common to use a stepping motor for the focus lens group of the inner focus lens system.

The stepping motor rotates in perfect synchronization with the stepping pulse output from the lens controlling microcomputer and the stepping angle per pulse is constant, so that the stepping motor has high speed response, stopping accuracy, and position. It is possible to obtain accuracy.

Further, when a stepping motor is used,
Since the rotation angle with respect to the number of step pulses is constant, the step pulse can be used as it is as an increment type encoder, and there is an advantage that no special position encoder needs to be added.

As described above, when the zooming operation is performed while keeping the focus by using the stepping motor, the locus information of FIG. It is also necessary to read the locus information according to the position or moving speed of the variable power lens and move the focus lens based on the information.

FIG. 4 is a diagram for explaining an example of a trajectory tracking method previously devised by the present applicant. FIG.
In (a), z0, z1, z2, ... z (m) indicate the zoom lens positions, and a0, a1, a2, ... a (m) and b0, b1, b2 ,. .b (m)
Are representative loci stored in the lens control microcomputer.

Further, p0, p1, p2, ... P (m) are loci calculated based on the above two loci. The formula for calculating this locus is shown below.

P (k + 1) = a (k + 1) + (p (k) -a (k)) / (b (k) -a (k)) * (b (k + 1) -a (k + 1)) (1) If (p (k) -a (k)) = α and (b (k) -a (k)) = β,
Equation (1) becomes p (k + 1) = a (k + 1) + α / β * (b (k + 1) -a (k + 1)) (1) '.

According to the equation (1), for example, in FIG.
When the focus lens is located at p0, a ratio at which p0 internally divides the line segment b0-a0 is obtained, and a point at which the line segment b1-a1 is internally divided according to this ratio is defined as p1. Then, the moving speed of the focus lens for keeping the focus can be known from the position difference of p1−p0 and the time required for the variable power lens to move from z0 to z1.

Incidentally, FIG. 4B shows a state in which the representative loci shown in FIGS. 3 and 4A are stored in a table in the memory.

Next, a case will be described in which the stop position of the variable power lens is not limited to only the boundary where the stored representative trajectory data is owned.

FIG. 5 is a diagram for explaining an interpolation method in the position of the variable power lens (that is, in the horizontal axis direction).
A part of (a) is extracted and the zoom lens position is arbitrarily set.

In FIG. 5, the vertical axis and the horizontal axis respectively show the focus lens position and the zoom lens position, and the representative locus position (focus lens position with respect to the zoom lens position) stored in the lens control microcomputer is Zoom lens positions z0, z1, ... z (k-1), z (k) ... z (m), and the focus lens position at that time is a0, a1, ... a (k -1), a (k) ... a (m) b0, b1, ... b (k-1), b (k) ... b (m).

Now, the zoom lens position is not on the zoom boundary.
If z (x) and the focus lens position is p (x),
When a (x) and b (x) are calculated, a (x) = a (k) − (z (k) -z (x)) * (a (k) -a (k-1)) / ( z (k) -z (k-1)) ... (2) b (x) = b (k) − (z (k) -z (x)) * (b (k) -b (k-1) ) / (Z (k) -z (k-1)) ... (3).

That is, the current zoom lens position and two zoom boundary positions that sandwich the zoom lens position (for example, z (k) and z (k-1) in FIG. 5).
The same among the four representative locus data stored (a (k), a (k-1), b (k), b (k-1) in Fig. 5) according to the internal division ratio obtained from It is possible to obtain ax and bx by internally dividing the object distance at the object ratio.

Then, according to the internal division ratio obtained from a (x), p (x), b (x), four stored representative data (in FIG. 5, a
(k), a (k-1), b (k), b (k-1)) with the same focal length
As shown in Eq. (1), by internally dividing by the internal division ratio, p (k), p
(k-1) can be obtained.

At the time of zooming, from the position difference between the follow-up focus position p (k) and the current focus position p (x), and the time required for the zoom lens to move from z (x) to z (k). , The moving speed of the focus lens for keeping the focus is known. A trajectory tracking method using the above interpolation has been devised.

[0031]

However, the stored cam locus is from infinity to the closest focusing position, and is within the table area shown by the hatched portion in FIG.

However, if the temperature around the lens changes and the focus changes, the infinite focus position may shift to the super infinity side as shown in FIG. 6, and the closest focus position is also very close. It may shift to the side.

In this case, if the interpolation method is performed, since there is no memory cam locus in super infinity, the stored infinite cam locus will be traced, and if the zoom is made to an infinite subject depending on the temperature change, focusing cannot be achieved. The problem to say arises. This also applies to the near side.

Further, the phenomenon that the stored design cam locus and the in-focus position deviate from each other is caused not only by the focus shift due to the temperature of the lens but also by the error in manufacturing such as the positional accuracy of each lens group and the variation of the focal length. Sometimes.

Therefore, an object of the present invention is to provide a lens control device capable of maintaining the focus during the zoom operation even when the focus position is not within the stored cam locus. It is in.

[0036]

In order to solve the above-mentioned problems, according to the invention described in claim 1 of the present application, a first lens group for performing a zooming operation, and the first lens group A second lens group for correcting the movement of the focal plane during movement, a driving means for moving the first and second lens groups respectively in parallel with the optical axis, and a position of the first lens group. And a storage unit that stores the focus position of the second lens unit with respect to the first lens unit according to the object distance, and a second unit that corrects the focal plane when the first lens unit moves based on the information stored in the storage unit. The moving speed of the lens group is calculated, and if the focusing position of the second lens group exists outside the focusable moving range of the second lens group stored in the storage means, the storage is performed. The movement of the first lens group based on the information stored in the means. Configuration to which an arithmetic means for calculating a moving speed of the second lens group for correcting the serial focal plane.

According to the invention of claim 2 of the present application, the first lens group for performing the variable power operation and the first lens group for correcting the movement of the focal plane when the first lens group is moved. The second lens group, the driving means for moving the first and second lens groups respectively in parallel with the optical axis, and the focus position of the second lens group with respect to the position of the first lens group, A storage unit that stores the distance according to the distance, and a moving speed of the second lens unit that corrects the focal plane when the first lens unit is moved are obtained from the information stored in the storage unit, and stored in the storage unit. The first lens group is present at a position other than the position corresponding to the stored position information, and the second lens group stored in the storage means is outside the focusable movement range of the second lens group. If the in-focus position of the lens group exists, the memory hand Information stored in the result, a configuration in which an arithmetic means for obtaining the moving speed of the second lens group that corrects the focal plane during the movement first lens group.

[0038]

According to the first aspect of the present invention, the moving speed of the second lens group for correcting the focal plane when the first lens group is moved is obtained from the information stored in the storage means. When the in-focus position of the second lens group exists outside the in-focus movable range of the second lens group stored in the storage means, the information stored in the storage means determines the first position. The moving speed of the second lens group for correcting the focal plane when the first lens group moves is obtained by calculation.

According to the second aspect of the present invention, the first lens group is present at a position other than the position corresponding to the position information stored in the storage means, and the information stored in the storage means is used. Then, the moving speed of the second lens group for correcting the focal plane when the first lens group is moved is obtained, and the second lens group is stored outside the in-focus moving range of the second lens group. When the in-focus position of the second lens group exists, the moving speed of the second lens group for correcting the focal plane during the movement of the first lens group is determined by the information stored in the storage means. It is calculated.

[0040]

Embodiments of the camera of the present application will be described in detail below with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing the construction of the first embodiment of the camera of the present invention.

In the figure, 101, 102, 103,
Reference numerals 104 and 105 respectively denote elements that constitute an inner focus type lens system, and include a fixed front lens group, a second lens group (magnifying lens) for performing zooming, an aperture stop, and a fixed third lens group. It is a lens group and a fourth lens group (referred to as a focus lens) having both a competition function and a focusing function. Elements corresponding to those in FIG. 2 are designated by the same reference numerals.

The image light transmitted through this lens system is imaged on the image pickup surface 106a of the image pickup device 106, photoelectrically converted into an image pickup signal, and output.

Reference numeral 107 is an amplifier or impedance converter, and 108 is a camera signal processing circuit for subjecting the image pickup signal output from the amplifier 107 to a standardized video signal by subjecting it to a predetermined signal processing. The generated video signal is amplified to a specified level by an amplifier 109, and an LCD (liquid crystal display) as an electronic viewfinder.
After being processed by the display circuit 110, the captured image is displayed on the LCD 111.

On the other hand, the image pickup signal amplified by the amplifier 107 is sent to the aperture control circuit 112 and the AF evaluation value processing circuit 114.

In the aperture control circuit 112, the IG driver 113 and the IG meter 114 are selected according to the video signal input level.
Is driven to control the aperture amount of the diaphragm 103 to adjust the light amount.

In the AF evaluation value processing circuit 115, in response to the gate signal from the distance measurement frame generation circuit 117, only the video signal corresponding to the distance measurement frame is extracted from the image pickup screen, and the focus state is also detected. The focus detection operation is performed by extracting only the high-frequency component that changes.

Reference numeral 116 denotes an AF processing microcomputer (hereinafter referred to as an AF microcomputer), which performs drive control of various lenses and ranging frame control for changing the ranging area according to the AF evaluation signal strength. There is. The AF microcomputer corresponds to the calculating means of the present invention. The storage means of the present invention is also constituted by a ROM provided in the AF microcomputer, and stores the representative cam loci as shown in FIGS. 3 and 4.

Further, the AF microcomputer 116 is in data communication with a system control microcomputer (hereinafter referred to as "syscon") 122 which controls the entire apparatus, and the syscon 122 includes a zoom switch (SW) 12
Operation information of 3 (a unitized zoom SW outputs a voltage according to the rotation angle of the operation member, and variable speed zoom is performed according to this output voltage) is read by A / D conversion or the like. The zooming information controlled by the AF microcomputer 116 during zooming, focal length, and other zooming operation information are exchanged with each other.

Reference numerals 118 and 120 denote AF microcomputer 1 respectively.
A zoom driver, a focus driver 119, and a zoom driver 119 for outputting drive energy to a lens driving motor in accordance with drive commands for the variable-magnification lens 102 and the focus lens 105 output from the zoom lens 1, respectively.
02 and a focus motor for driving the focus lens 105.

Hereinafter, assuming that the lens driving motor is a stepping motor, a method of driving the motor will be described.

The AF microcomputer 116 determines the drive speeds of the zoom motor 119 and the focus motor 121 by a program process, and uses them as the rotation frequency signals of the stepping motors to drive the zoom motor 119.
8. Send to the driver 120 for driving the focus motor 121.

The drive / stop commands for the zoom motor 119 and the focus motor 121, and the rotational direction command for each motor are also issued to the zoom driver 118 and the focus driver 120.
I am sending it to.

The drive / stop signal and the rotation direction signal are mainly used for the zoom motor 119.
Depending on the state of the unit 123, the focus motor 12
Regarding No. 1, the drive command is determined by the processing in the AF microcomputer 116 during the AF operation and the zoom operation.

Each driver responds to the rotation direction signal by 4
By setting the phases of the motor excitation phases of the two phases to forward rotation and reverse rotation, and changing the applied voltage (or current) of the four motor excitation phases according to the received rotation frequency signal, and outputting. The output to each motor is turned on / off in response to the drive / stop command while controlling the rotation direction and rotation frequency of the motor.

FIG. 7 is a flowchart showing the control operation for carrying out the present invention, which is processed in the lens control AF microcomputer 116.

S1 indicates the start of processing. S2 is an initialization routine, which is a RAM in the AF microcomputer 116.
And reset processing of various ports.

S3 is an intercommunication routine with the system controller 122, in which operation information of the zoom SW unit 123 and zooming operation information such as the zoom lens position are exchanged.

S4 is an AF processing routine, which performs automatic focus adjustment processing according to the level change of the high frequency component in the image pickup signal as the focus state evaluation signal. Specifically, the focus lens 1 is set so that the level of the high frequency component becomes the maximum value.
05 is controlled.

S5 is a zoom processing routine, which is a processing routine for controlling the focus lens 105 for maintaining the in-focus state and executing the compensator operation while the zoom SW 123 is operated to perform the zooming operation. In this routine, the driving direction and driving speed of the focus lens 105 for tracing the cam locus as shown in FIG. 3 are calculated.

The zoom processing routine at S5 will be described later in detail with reference to the flowchart of FIG.

In step S6, of the driving directions and driving speeds of the variable magnification lens 102 and the focus lens 105 calculated in the processing of steps S5 to S6 in accordance with the AF operation or the variable power operation, etc.
This is a routine for selecting and setting which one to use.

In S7, control signals are output to the motor drivers 118 and 120 in accordance with the driving directions and driving speed information of the variable magnification lens 102 and the focus lens 105, which are determined in the processing of S6, and the lens is driven / stopped. To control. After the processing of S7 ends, the process returns to S7.

The series of processes shown in the flowchart of FIG. 7 are executed in synchronization with the vertical synchronization period (waiting for the next vertical synchronization signal in the process of S3).

FIG. 8 is a flow chart of control for implementing the present invention, showing a subroutine executed in the process of S5.

When the processing is started, S51 sets the speed of the variable magnification lens 102 based on the information of the zoom SW 123 obtained by communication with the syscon 122, and reads the variable magnification lens position at that time.

In S52, it is determined whether or not zooming is in progress. If zooming is not in progress, it is defined in S53 whether or not the focus position at that time is stored in the table, that is, the stored position information. Determine whether it is within the area.

If it is within the stored area, the process proceeds to S54, and the flag indicating that it is outside the area with the stored information is set to 0, and the positions of the variable magnification lens 102 and the focus lens 105 at that time are set. , Set a focusing cam locus from the stored representative cam table.

The focus cam locus is the variable magnification lens 10 at the time of focus.
2 shows where the focus lens 105 exists on the representative cam table, and if it is within the area, FIG.
When the focus is p0 in (a), the ratio that p0 internally divides the line segment b0-a0 (β) is p0-a0 / b0-a0 = α / β (interpolation) Where a0 = A (0,0), b0 = A (1,0)
Therefore, when m = 0, it becomes a point that α / β between n = 0 and 1, and the locus connects that point from wide to tele (m = 0, 1, ... M). Therefore, the focus cam locus can be set by calculating n, α, and β from the zoom and focus lens positions at that time.

When it is determined in S53 that the focus position at that time is not within the stored area, the process proceeds to S55, and the flag indicating that it is outside the area is set to 1 and the change at that time is made. The focus cam locus is selected from the positions of the double lens 102 and the focus lens 105 and the stored representative cam locus table.

The in-focus cam locus shows where in the representative cam locus table the variable magnification lens 102 and the focus lens 105 exist at the time of focusing. When the focus is p0 ', p0' is the line segment b0-a
The ratio of 0 (β) to the outside is a0-p0 '/ b0-a0 = α' / β (extrapolated), and a0 = A (0,0) and b0 = A (1 , 0)
Therefore, when m = 0, the point between n = 0 and 1 is extrapolated by α ′ / β, and the locus connects the point from wide to tele (m = 0, 1, ... M).

Therefore, the focus cam locus can be set by calculating n, α ', and β from the positions of the variable power lens 102 and the focus lens 105 at that time.

On the other hand, if it is determined in S52 that the scaling operation is being performed, the process proceeds to S56, in which fl is set.
If ag = 0, the process proceeds to S57, and since it is within the area of the storage table, n, β of the focus cam locus set in the process of S54 are used to perform the interpolation calculation of the equation (1) ′. And then
Target position p (n + 1) of the focus lens 105 during zooming operation
Is calculated.

In the process of S56, if flag = 1, the process proceeds to S58, and since it is outside the area of the storage table, n, of the focusing cam locus set in the process of S55 is set.
Using α'and β, p (k + 1) '= a (k + 1)-(a (k) -p (k)') / (b (k) -a (k)) * ( b (k + 1) -a (k + 1)) (4) (a (k) -p (k) ') = α, (b (k) -a (k)) = β, (Four)
The formula is the extrapolation of p (k + 1) '= a (k + 1) -α' / β * (b (k + 1) -a (k + 1)) (4) '. , Focus lens 10 during zooming operation
The target position p (k + 1) 'of 5 is calculated.

Then, in the processing of S59, this p (k + 1) -p
Based on the position difference of (k) or p (k + 1) '-p (k) and the time required for the zoom lens to move from z (k) to z (k + 1), Set the moving speed (direction and speed) of the focus lens to maintain focus.

The above equation (4) is an equation for the case where the in-focus position is outside the region on the ultra-infinity side, and when it is on the ultra-close side, p (k + 1) '= b (k + 1) ＋ (p (k) '-b (k)) / (b (k) -a (k)) ＊ (b (k + 1) -a (k + 1)) …… (5) (a If (k) -p (k) ') = α and (b (k) -a (k)) = β, then (5)
The equation is p (k + 1) '= b (k + 1) + α' / β * (b (k + 1) -a (k + 1)) (5) ', and from equation (5) Focus target position during zoom operation
Calculate p (k + 1) '.

According to the above method, as shown in FIG. 6, the focus position is out of the storage table area due to the focus deviation due to the temperature of the lens, the positional accuracy of each lens group, the variation of the focal length, and other errors that occur during manufacturing. Even when it is, the moving target position of the focus lens 105 is corrected, and the in-focus state can be reliably maintained during the zooming operation.

(Second Embodiment) In the first practical example described above, the case where the variable power lens is on the cam locus indicated by the stored information in the storage cam table has been described. Next, the variable power lens is stopped. A case will be described in which the restriction that the position is only on the boundary that owns the stored representative trajectory data is removed so that the position does not have to be on the boundary of each area having the representative trajectory data.

FIG. 5 is a diagram for explaining the extrapolation method in the direction of the zoom lens position, that is, in the direction of the horizontal axis as seen in FIG. 3. A part of FIG. 4A is extracted to determine the zoom lens position. It is optional.

As described above, in FIG. 5, when the variable-magnification lens position is at z (x) that is not on the zoom boundary, when a (x) and b (x) are calculated, the above (2) and (3) are obtained. It is represented by a formula.

That is, the current zoom lens position and two zoom boundary positions that sandwich the zoom lens position (for example, z (k) and z (k-1) in FIG. 5).
The same among the four representative locus data stored (a (k), a (k-1), b (k), b (k-1) in FIG. 5) according to the internal division ratio obtained from It is possible to obtain ax and bx by internally dividing the object distance at the object ratio.

If the focus position is within the area, a (x), p
According to the internal division ratio obtained from (x), b (x), four representative data stored (in FIG. 5, a (k), a (k-1), b (k), b (k- Among the 1)), p (k) and p (k-1) can be obtained by internally dividing the one having the same focal length with the internal division ratio as shown in the equation (1).

During the zooming operation, the position difference between the following focus lens position p (k) and the current focus lens position p (x) and the zooming lens move from z (x) to z (k). The moving time of the focus lens for keeping the focus can be known from the time required for.

If the focus position is out of the area, a (x),
4 stored according to the external ratio obtained from p (x) ', b (x)
One representative data (a (k), a (k-1), b (k), b (k-1) in Figure 5)
Among them, p (k) 'and p (k-1)' can be obtained by externally dividing those having the same focal length by the external division ratio as shown in equation (4) or (5).

During zooming, the position difference between the following focus lens position p (k) 'and the current focus lens position p (x)' and the zoom lens moves from z (x) to z (k). The moving speed of the focus lens for maintaining the in-focus can be known from the time required for.

Therefore, even when the in-focus position is outside the area of the storage table due to an error that occurs during manufacturing, such as focus deviation due to lens temperature, positional accuracy of each lens group, and variation in focal length, zooming is performed again. Regardless of the position of the lens, the movement target position of the focus lens 105 is corrected, and the in-focus state can be reliably maintained during the zooming operation.

[0087]

As described above, according to the invention described in claim 1 of the present application, the second lens stored in the storage means is outside the focusable movement range of the second lens group. When the focus position of the group exists, the moving speed of the second lens group for correcting the focal plane when the first lens group moves is calculated based on the information stored in the storage means. Since the calculated cam locus is from infinity to the closest focusing position, the temperature around the lens changes and the infinite focusing position shifts to the super infinity side, or the closest focusing position. Even if the focal point shifts to the very close side, or if the in-focus position deviates from the stored cam locus due to manufacturing errors such as positional accuracy of each lens group or focal length variation, The in-focus state can be reliably maintained during operation.

According to the second aspect of the invention, the first lens group exists at a position other than the position corresponding to the position information stored in the storage means, and the second lens group stored in the storage means. When the in-focus position of the second lens group exists outside the in-focus movable range of the second lens group, the focal plane when the first lens group is moved is determined by the information stored in the storage means. Since the moving speed of the second lens group for correction is obtained by calculation, the stored cam locus is from infinity to the closest focusable area, the temperature around the lens changes, and Even if the focus position shifts to the ultra-infinity side or the closest focus position shifts to the ultra-close end side, the focus position is also affected by manufacturing errors such as positional accuracy of each lens group and focal length variation. However, even if it deviates from the stored cam locus, It can be maintained reliably focus state during operation.

Further, according to the invention described in each of the claims, errors that occur in manufacturing such as temperature focus deviation, positional accuracy of each lens group, and variation of focal length can be achieved without increasing the capacity of the storage cam locus in the memory. Thus, even if the focus position deviates from the stored cam locus, the focus can be maintained during the zoom operation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a lens control device of the present invention.

FIG. 2 is a diagram showing a configuration of an inner focus type lens.

FIG. 3 is a diagram showing a cam locus showing, for each object distance, the position of the focus lens that maintains the in-focus state with respect to the position of the variable power lens in the inner focus type lens.

FIG. 4 is a diagram for explaining an example of a cam locus tracking method.

FIG. 5 is a diagram for explaining a calculation for causing the focus lens to follow a position between stored cam loci.

FIG. 6 is a diagram showing a focusable range based on a cam locus stored in a memory.

FIG. 7 is a flowchart showing a processing operation executed in the AF microcomputer according to the present invention.

FIG. 8 is a flow chart showing the control operation of the focus lens when the focus lens is located outside the focusable range based on the cam locus stored in the memory according to the present invention.

[Explanation of symbols]

 102 variable magnification lens 105 focus lens 106 image sensor 108 camera signal processing circuit 115 AF evaluation area processing circuit 116 AF microcomputer 118 zoom driver 119 zoom motor 120 focus driver 121 focus motor 123 zoom SW unit

Claims (2)

[Claims] 1. A first lens group for performing a zooming operation, a second lens group for correcting movement of a focal plane when the first lens group moves, and the first and second lens groups. Driving means for moving the respective lens groups in parallel with the optical axis, storage means for storing the in-focus position of the second lens group with respect to the position of the first lens group according to the subject distance, and the storage means. The moving speed of the second lens group that corrects the focal plane when the first lens group is moved is obtained from the information stored in the first lens group, and the focus of the second lens group stored in the storage unit is determined. When the in-focus position of the second lens group exists outside the possible movement range, the focal plane when the first lens group is moved is corrected based on the information stored in the storage means. For calculating the moving speed of the second lens group for Lens control apparatus, characterized in that the. 2. A first lens group for performing a zooming operation, a second lens group for correcting the movement of the focal plane when the first lens group moves, and the first and second lens groups. Driving means for moving the respective lens groups in parallel with the optical axis, storage means for storing the in-focus position of the second lens group with respect to the position of the first lens group according to the subject distance, The moving speed of the second lens group that corrects the focal plane when the first lens group is moving is calculated from the information stored in the means, and the moving speed other than the position corresponding to the position information stored in the storage means is obtained. When the first lens group is present and the in-focus position of the second lens group is outside the in-focus movable range of the second lens group stored in the storage means, , The information stored in the storage means Lens control device characterized by comprising a calculating means for calculating the moving speed of the second lens group that corrects the focal plane during group movement of the lens.