JP2001208955A - Lens controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make zooming performable while maintaining accurate focusing in the case of performing zooming in the off-state of AF. SOLUTION: When the mode is switched from an automatic focusing mode to a manual focusing mode in the case of zooming while maintaining focusing by using a focusing lens locus table in which the focusing position of a focus compensating lens to the discrete position of a variable power lens is previously stored in accordance with a discrete substance distance, a new focusing locus is arithmetically calculated based on the focusing locus just before switching and is inhibited from being arithmetically calculated in the midst of zooming thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens control apparatus for an inner focus type lens system.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram of a conventionally known inner focus type lens system. As shown in FIG. 6, an inner focus type lens system 1 includes a first fixed lens 2 which is arranged along the optical axis sequentially from the subject side on the left side of FIG. A variable power lens 3 for moving the zoom lens to zoom, a diaphragm 4, and a second
It has a fixed lens 5 and a focus compensating lens 6 having a so-called competing function for performing focus adjustment by moving in parallel with the optical axis and performing correction when the focal plane moves due to zooming. I have. Then, the optical subject image formed by the lens system 1 is formed on the image pickup surface 7a of the image pickup device 7, is subjected to photoelectric conversion, and is output as a video signal.

In such an inner focus type lens system 1, since the focus compensating lens 6 has both the competing function and the focus adjusting function as described above, even if the focal lengths are equal, the focus on the image pickup surface 7a. The position of the focus compensating lens 6 for performing the operation differs depending on the subject distance.

That is, when the subject distance is changed at each focal length, the position of the focus compensating lens 6 for focusing on the imaging surface 7a is plotted continuously as shown in FIG. Therefore, in order to perform zooming without blur, during zooming, the focus lens locus shown in FIG. 7 is selected according to the subject distance, and the focus compensating lens 6 is moved according to the selected focus lens locus. There is a need.

[0005] In the front lens type lens system, a compensating lens independent of the variable power lens is provided, and the variable power lens and the compensating lens are connected by a mechanical cam ring. Therefore, for example, when a knob for manual zoom is provided on the cam ring and the focal length is manually changed, no matter how fast the knob is moved,
The cam ring rotates following this, and the variable power lens and the compensating lens move along the cam groove of the cam ring. Therefore, if the focus lens is in focus, the above operation does not cause blur.

On the other hand, in the lens system 1 of the inner focus type, as described above, in order to perform zooming without blur, it is necessary to move the focus compensating lens 6 along the locus shown in FIG. For this reason, a plurality of focus lens trajectory information corresponding to the subject distance as shown in FIG. 7 is stored in the lens control microcomputer in some form (the trajectory itself or a function using the lens position as a variable), and the focus control is performed. A trajectory tracking method of selecting a focus lens trajectory according to the positions of the lens 6 and the variable power lens 3 and performing zooming while following the selected focus lens trajectory is generally adopted. The details of the trajectory tracking method will be described later.

At this time, in order to accurately control the focus by the focus compensating lens 6 and completely eliminate the blur, it is necessary to detect the positions of the variable power lens 3 and the focus compensating lens 6 to some extent accurately. In particular, as is clear from FIG. 7, when the variable power lens 3 moves at a constant speed or a speed close thereto, the inclination of the focusing lens locus to be followed by the focus compensating lens 6 changes every moment due to the change in the focal length. ing. This indicates that the moving speed and the moving direction of the focus compensating lens 6 change every moment. In other words, the actuator for the focus compensating lens 6 has an accurate speed response from 1 Hz to several hundreds Hz. Must be done.

In order to satisfy such demands, it is becoming common to use a stepping motor as an actuator for the focus compensating lens 6. The stepping motor rotates in full synchronization with the stepping pulse output from the lens control microcomputer or the like, and the stepping angle per pulse is constant, so that high speed responsiveness, stopping accuracy, and position accuracy can be obtained. Because. Furthermore, when a stepping motor is used, since the step angle with respect to the step pulse is constant, the step pulse can be used as it is as an increment type position encoder, and there is no need to add a special position encoder. There is also.

Next, a conventional example of the above-described trajectory tracking method for performing a variable power operation while maintaining focus in the inner focus type lens system 1 will be described with reference to FIG.

[0010] In FIG. 8, the vertical axis indicates the position of the focusing lens 6, and the horizontal axis indicates the position of the variable power lens 3. Further, z0, z1, z2,.
, A0, a1, a2,... A11;
.., b11 correspond to two different object distances, and represent representative focusing lens trajectories that the focus compensating lens 6 should follow following the movement of the variable power lens 3. . The focusing lens trajectory information is stored in the control microcomputer as a focusing lens trajectory table.

As shown in FIG. 8, the focusing lens trajectory table stores only typical focusing lens trajectories corresponding to discrete object distances. In this case, if the stored focusing lens trajectory is traced as it is, the variable power operation cannot be performed while maintaining the focus. Therefore, when the subject distance is not stored, the focusing lens locus corresponding to the unstored subject distance is calculated based on the stored focusing lens locus. P0, p1, p2,... P1 in FIG.
Reference numeral 1 denotes the calculated focusing lens locus. This p0, p
Focusing lens trajectories such as 1, p2,.

[0012]

## EQU1 ## p (n + 1) = | b (n + 1) -a (n + 1)
| × | p (n) −a (n) | / | b (n) −a (n) |
+ A (n + 1).

According to Equation 1, for example, in FIG. 8, when the focus compensating lens 6 is at the position of p0, p0
Calculates a ratio that internally divides the line segment “b0-a0”, and sets a point that internally divides “b1-a1” in accordance with the internal division ratio as p1. From the position difference between the points p1 and p0 and the time required for the variable power lens 3 to move from z0 to z1, the moving speed of the focus compensating lens 6 for maintaining focus is obtained.

When the variable power lens 3 moves from the telephoto to the wide direction, as shown in FIG. 7, since the trajectory of the focusing lens that has been displaced converges, the trajectory follow-up method described above is used. Scorching can be maintained. However, since the focus compensating lens 6 located at the convergence point does not know which focusing lens trajectory to follow from the wide-angle direction to the telephoto direction, focusing cannot be maintained by the similar trajectory tracking method.

Therefore, the contrast method (hill climbing method)
The focus lens trajectory is selected to minimize the front focus and rear focus information (blurring information) obtained during the automatic focus adjustment operation (AF), and zooming is performed while following the focus compensating lens 6 based on the focus lens trajectory. A scheme has been proposed.

However, in this method, the focus lens locus cannot be selected when the AF function is turned off. Therefore, when zooming is performed with the AF function turned off, focusing is maintained as follows.

That is, when the AF function is off, every time zooming from the telephoto to the wide direction in which focus can be maintained, z0, z1, z2,... Z11 of the variable power lens 3 in FIG.
Position p0, p of focus compensating lens 6 for each position
1, p2,..., P11 (in-focus lens locus) are calculated and sequentially stored in the memory of the microcomputer. Then, when zooming from wide to telephoto, the stored position of the focus compensating lens 6 is calculated. While reading, the trajectory traced during zooming from the telephoto to the wide direction is traced in the opposite direction.

[0018]

However, in the above-mentioned conventional example, z0, z10, z2,.
It is necessary to calculate the focusing positions p0, p1, p2,... p11... of the focusing lens 6 for each position of z11... and store them separately from the focusing lens trajectory table. In order to improve the accuracy of following the lens trajectory, a large number of in-focus positions of the focusing lens 6 are calculated and calculated.
Since it is necessary to store the information, it is disadvantageous in terms of the capacity of the microcomputer for lens control and the processing time, and the processing is complicated.

Further, since the focusing lens trajectory is stored each time zooming is performed from the telephoto to the wide direction, if zooming from the telephoto to the wide direction or from the wide to the telephoto direction is repeated many times in the AF off state, Due to the error of the focusing lens trajectory following operation, the focusing lens trajectory having the object distance different from the initially stored object distance is stored, and the blur is gradually widened.

Further, due to the storage method, in the conventional example, even if the stored focusing position is connected, the focusing lens locus in the optical design may not be overlapped, and blurring occurs during zooming.

The present invention has been made under such circumstances, and its object is to save processing capacity and processing time and maintain accurate focusing when performing zooming in the AF off state. That is, zooming can be performed.

[0022]

In order to achieve the above object, a first aspect of the present invention provides a first lens for performing a zooming operation and a correction of a movement of a focal plane when the first lens is moved. A lens for moving the first lens and the second lens independently of each other in parallel with an optical axis; and a second lens moving means for moving the first lens with respect to a discrete position of the first lens. A focus position storage means for storing a focus position of the lens in advance according to a discrete subject distance;
And a subject distance specifying means for specifying a focus trajectory of the second lens based on the current position of the second lens and information stored in the focus position storage means, When the mode is switched from the automatic focus adjustment mode to the manual focus adjustment mode, a new focus trajectory is specified based on the focus trajectory specified by the subject distance specifying means immediately before the switching, and the lens moving means sets After the first lens is moved and the zooming operation is performed, there is provided control means for prohibiting updating of the focus locus by the subject distance specifying means.

According to a second aspect of the present invention, there is provided a first lens for performing a zooming operation, a second lens for correcting a movement of a focal plane when the first lens is moved, and A lens moving means for independently moving the first lens and the second lens in parallel with the optical axis; and trajectory information of a focus position of the second lens with respect to the first lens position in advance according to a subject distance. The movement trajectory of the second lens is calculated based on the stored focus position storage means, the current positions of the first lens and the second lens, and the trajectory information stored in the focus position storage means. A subject distance specifying unit that performs switching from the automatic focus adjustment mode to the manual focus adjustment mode, wherein the second lens specified by the subject distance specifying unit immediately before the switching is performed. Move A control means for calculating a new movement trajectory based on the trace, and prohibiting the subject distance identification means from calculating the movement trajectory after the lens movement means starts the zooming operation by moving the first lens. are doing.

Further, in the third invention, the control means according to the second invention, when switching from the automatic focus adjustment mode to the manual focus adjustment mode, uses the movement locus specified immediately before the switching. It is configured to perform an internal division ratio calculation on the basis of this and calculate a new movement locus.

[0025]

In the first, second, and third inventions, the first lens performs a zooming operation, and the second lens functions as a lens that corrects the movement of the focal plane when the first lens moves. .
Further, the lens moving means moves the first lens and the second lens independently of each other in parallel with the optical axis.

The focus position storage means of the first invention has a first
The in-focus position of the second lens with respect to the discrete position of the first lens is stored in advance in accordance with the discrete object distance, and the first lens is stored in the in-focus position storage means of the second and third inventions. Trajectory information of the in-focus position of the second lens with respect to the position is stored in advance according to the subject distance.

According to the first aspect of the present invention, the object distance specifying means includes:
The focus locus of the second lens is specified based on the current position of the second lens and the current position of the second lens and the information stored in the focus position storage means.

The subject distance specifying means according to the second and third aspects of the present invention uses the second position based on the current position of the first lens and the second lens and the trajectory information stored in the focus position storage means. The movement locus of the lens is calculated.

The control means of the first invention, when switched from the automatic focus adjustment mode to the manual focus adjustment mode, performs a new focusing based on the focusing locus specified by the subject distance specifying means immediately before the switching. After the trajectory is specified and the first lens is moved by the lens moving means to perform the zooming operation, the updating of the focus trajectory by the subject distance specifying means is prohibited.

Further, the control means according to the second invention, when the mode is switched from the automatic focus adjustment mode to the manual focus adjustment mode, the movement trajectory of the second lens specified by the subject distance specifying means immediately before the switching. A new trajectory is calculated based on the calculated trajectory, and after the zooming operation by moving the first lens is started by the lens moving unit, the calculation of the trajectory by the subject distance specifying unit is prohibited.

When calculating a new movement trajectory as in the second invention, the control means of the third invention, when switching from the automatic focusing mode to the manual focusing mode, immediately before the switching. A new moving trajectory is calculated by performing the internal division ratio calculation based on the moving trajectory specified in (1).

[0032]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram schematically showing a video camera provided with a lens control device according to one embodiment of the present invention.

In FIG. 1, reference numeral 10 denotes an inner focus type lens system.
In the figure, a first fixed lens 11 is arranged along the optical axis in order from the subject side on the left side to the right side, a variable power lens 12 that moves in parallel with the optical axis to perform zooming, an aperture 13, and a second fixed part. The lens 14 includes a focus compensating lens 15 having a so-called competing function for performing focus adjustment by moving in parallel with the optical axis and performing correction when the focal plane moves due to zooming.

The image of the optical subject by the lens system 10 is transferred to the image pickup device 1 composed of a CCD or the like.
The image is formed on the imaging surface 16a of No. 6, is photoelectrically converted, and is output as a video signal. This video signal (electric signal)
The signal is amplified by an amplifier (or impedance converter) 17, the output amplitude is kept constant by an AGC (automatic gain control) circuit 18, and only a high frequency component is extracted by a filter 19. Then, the signal processing circuit 20 performs signal processing such as obtaining the intensity of a high frequency component or the blur width detection intensity in order to perform AF (autofocus) processing on the video signal from the filter 19, and performs lens control. Output to the microcomputer 21.

The variable power lens 12 and the focusing lens 15 are moved by lens moving means 22 and 23, respectively. The lens moving units 22 and 23 have stepping motors 22a and 23a and drivers 22b and 23b (hereinafter, a stepping motor for moving the variable power lens 12 is a zoom motor and a focus compensating lens 15).
The stepping motor for driving is called a focus motor.) These zoom motor 22a and focus motor 2
Racks 22d and 23d are meshed with output shafts 22c and 23c, respectively, which are directly connected to 3a.
2d and 23d are fixed to the variable power lens 12 and the focus compensating lens 15, respectively.

Then, according to the movement command signals (direction signals s1, s2, speed signals s3, s4) output from the lens control microcomputer 21, the driving energy is supplied from the drivers 22b, 23b to the zoom motor 22a, the focus motor 2
3a, the output shafts 22c and 23c are rotated to rotate the variable power lens 12 and the focus compensating lens 15 integrally with the racks 22d and 23d in parallel with the optical axis (in the directions of arrows A and B in the figure). Moving.

The positions of the variable power lens 12 and the focusing lens 15 are determined by lens position detecting means 24 and 25, respectively.
Is detected by The lens position detecting means 24, 25
Photo sensors 24a, 25a and light shielding plates 24b, 25b
The photo sensors 24a and 25a are configured as a light emitting unit and a light receiving unit (not shown),
25b is fixed to the variable power lens 12 and the focus compensating lens 15, respectively.

When the variable power lens 12 and the focus compensating lens 15 move parallel to the optical axis, the light shielding plates 24b and 25b move integrally therewith, and the photo sensors 24a and
When the optical path between the light emitting unit and the light receiving unit 25a is blocked, the output signal of the light receiving unit is at a low level, and when not blocked, the output signal is at a high level.

Therefore, it is possible to detect whether or not the variable power lens 12 and the focus compensating lens 15 are at the reference position, using the position where the output signal of the light receiving section changes as the reference position. Then, the lens control microcomputer 21 can recognize the position of each lens based on the reference position, the lens moving speed, the lens moving direction, and the like.

The aperture 13 is driven by a driver 26 so as to maintain an appropriate exposure amount. That is, the aperture control circuit 27 detects the level of the output signal of the AGC circuit 18, and when the level is not a constant level (appropriate exposure amount), generates an aperture amount control signal for setting the level to a constant level. The aperture control signal is amplified by the second amplifier 28 and output to the driver 26, and the driver 13 drives the aperture 13 to obtain an appropriate exposure.

The aperture state of the aperture 13 is detected by an encoder 29, and the detection signal is amplified by a third amplifier 30 and converted into a signal readable by a lens control microcomputer 21 by a signal conversion circuit 31. It is output to the lens control microcomputer 21.

The lens control microcomputer 21 moves the wide-angle switch 32, the tele-switch 33 for moving the variable power lens 12 in the wide direction and the tele direction, and the focus compensating lens 15 in the infinity direction and the closest direction, respectively. Infinite switch 34, close switch 3
5. The AF switch 36 for setting the AF mode is connected. These switches and the lens control microcomputer 21
The power supply 38 is connected to the connection line via a pull-up resistor 37.

The lens control microcomputer 21 is preset with a focus lens trajectory table T as shown in FIG. 2 in which the contents of the focus lens trajectory of FIG. 7 are tabulated. That is, the focusing lens trajectory table T in FIG.
Focus Compensation Lens 1 corresponding to 2 discrete positions
5 is a table in which the in-focus positions of No. 5 are recorded for each subject distance, and n (0, 1,..., K,.
m) indicates a discrete subject distance, z (0, 1,..., k,... l) in the row direction (vertical direction in the figure) indicates the position of the discrete variable power lens 12, The positions of the discrete zoom lens 12 and the in-focus position of the focus compensating lens 15 corresponding to the subject distance are recorded at the intersections of. It should be noted that the subject distance becomes shorter in the right direction in the figure, where "0" indicates infinity and "m" indicates the closest 1 cm. Further, as for the position of the variable power lens, the zoom area becomes wider as it goes downward in the figure, and "0"
Indicates the telephoto end, and “l” indicates the wide end. Then, the focus position of the focus compensation lens 15, for example, A
0k indicates the focus position of the focus compensating lens 15 when the object distance is “0” and the position of the variable power lens 12 is “k”.

When performing zooming in the AF mode, the lens control microcomputer 21 selects a focus lens locus in the focus lens locus table T using the front focus and rear focus information, or Zooming is performed while calculating the focus lens position based on the focus lens locus. On the other hand, when performing zooming with the AF mode turned off, when a focusing operation is manually performed before zooming, the subject distance is specified, and the internal division ratio of Expression 1 corresponding to the subject distance is determined. During the zooming, the in-focus position of the focus compensating lens 15 is obtained from the formula 1 based on the internal division ratio, and the focus compensating lens 15 is made to follow.

Next, lens control when zooming is performed with the AF mode turned off will be described with reference to the flowcharts of FIGS. Note that the flowcharts of FIGS. 3 and 4 are subroutines, and are executed by a contrast method (hill-climbing method) in which automatic focus adjustment is controlled according to a focus voltage (sharpness of a video signal) before this flow is executed. AF mode processing is being executed. 3 and 4 are based on the premise that the variable power lens 12 stops only at discrete positions recorded in the focusing lens trajectory table T in FIG.

First, the lens control microcomputer 21 determines whether zooming is being performed by determining whether the wide switch 32 and the tele switch 33 are on or off (step S1). As a result, either the wide switch 32 or the tele switch 33 is turned on, and if zooming is being performed, the process proceeds to step S15 described below. On the other hand, if neither the wide switch 32 nor the tele switch 33 is turned on and the zooming is not being performed, it is determined whether the AF mode is set by determining whether the AF switch 36 is on or off ( Step S2). As a result, A
If the F switch 36 is turned on and the AF mode is set, the process returns to the main flow. Note that A
When the F mode is set, the AF not shown
Focus control is performed by the mode processing routine. on the other hand,
If the AF switch 36 is turned off and the AF mode is not set, it means that the manual focusing mode is currently set, and whether the manual focusing mode has been switched from the AF mode and set, or It is determined whether the manual focusing mode has been set for all the time (step S3). As a result, if the manual focusing mode has been set for a long time, it is determined whether or not the power focusing state is established by determining whether the infinite switch 34 and the close switch 35 are on / off (step S4). As a result, if either the infinite switch 34 or the close switch 35 is turned on and the power is in the focus state, it means that focus control is manually performed, and in this case, the process proceeds to step S5. On the other hand, if neither the infinite switch 34 nor the close switch 35 is turned on and the power is not in the power focus state, the process returns to the main flow in order to perform step S5 and thereafter after performing focus control manually.

If the AF mode has been switched from the AF mode to the manual focusing mode in step S3, it means that the focusing control has already been automatically performed in the AF mode before the switching, and step S4 is skipped. Then, the process proceeds to step S5.

In steps S5 to S14, the subject distance and the internal division ratio in equation 1 are specified. That is,
In step S5, an initial value “0” is set to a variable n for subject distance. Next, A (n, k) and A (n +
1, k), that is, the subject distance n, the current zoom lens position k, and the focus compensating lens position corresponding to the object distance n + 1 and the current zoom lens position k are read from the focusing lens locus table T (step S6). ).

Then, it is determined whether or not the current focus competition lens position f is equal to or larger than A (n, k) (step S7). Here, as shown in FIG. 7, at a predetermined zoom lens position, the focus competition lens position f
Increases as the subject distance approaches, so step S7 means that it is determined whether or not the current focus competition lens position f is closer than the subject distance n. I have. If it is determined in step S7 that the current focus competition lens position f is closer to the subject distance n, it is determined whether the current focus competition lens position f is smaller than A (n + 1, k). It is determined whether or not the current focus competition lens position f is on the infinity side of the subject distance n + 1 (step S8). As a result, when it is determined that the current focus competition lens position f is on the infinity side of the subject distance n + 1, it is determined that the current focus competition lens position f exists between the subject distances n and n + 1. That is, in this case, fA (n, k) is calculated, and the calculation result is stored as a constant α (step S9). Then, A (n + 1, k) -A (n, k) is calculated, and the calculation result is stored as a constant β (step S9). Next, the content of the current variable n is stored as a constant γ (step S10), and the process returns to the main flow.

When it is determined in step S7 that the current focus compensating lens position f is on the infinity side of the subject distance n, the current focus compensating lens position f is determined.
Means that the object distance is at a super-infinity subject distance. In this case, “0” is stored as the constant α (step S1).
2), proceed to step S10.

If it is determined in step S8 that the current focus compensating lens position f is closer than the object distance n + 1, the contents of the variable n for the object distance are stored in the focusing lens locus table T. It is determined whether or not it is not less than m which is the closest to (step S13). As a result, m
If not, the content of the variable n is incremented by 1 (step S14), and the process returns to step S6, thereby obtaining the current focus compensating lens position f as described above.
Between object distances.

On the other hand, if the content of the variable n for the subject distance is equal to or more than m, it means that the current focus compensating lens position f is located at a very close subject distance. As in the case of the distance, “0” is stored as the constant α (Step S12), and Step S10
Proceed to. These constants α, β, and γ are used as trajectory tracking parameters, as described later.

As described above, before zooming is performed, the object distance corresponding to the focus lens locus to be followed by the focus compensating lens 15 is specified.

If it is determined in step S1 that zooming is being performed, the process proceeds to step S15 as described above. In this step S15, the current zoom lens position z
= K is a discrete position (boundary position) recorded in the focusing lens trajectory table T. In this flow, as described above, it is assumed that the variable power lens 12 stops only at the boundary position, so that at the start of zooming, the variable power lens 12 is at the boundary position. It is determined whether or not the mode is set. As a result, if the mode is the AF mode, a later-described step S
Proceed to 22.

On the other hand, if the mode is not the AF mode, it is determined whether or not the tele switch 33 is turned on and zooming from wide to tele is being performed (step S17).
As a result, during zooming from wide to telephoto, the object distance γ and the focus compensating lens position A (γ, k + 1) corresponding to the variable power lens position k + 1 are read from the focusing lens trajectory table T and the constant a And a focus compensating lens position A (γ + 1, k +) corresponding to the subject distance γ + 1 and the zoom lens position k + 1.
1) is read from the in-focus lens locus table T and stored as a constant b (step S18). That is, on the focusing lens trajectory table T, the current zoom lens position k is obtained from the focusing lens trajectory data of the subject distance γ and the focusing lens trajectory data one closer to the subject distance γ.
One more telephoto focus compensating lens position data is read out and stored as constants a and b. On the other hand, during zooming from the telephoto to the wide direction, the object distance γ and the focus compensating lens position A (γ, k−1) corresponding to the zoom lens position k−1 are read from the focusing lens locus table T. Is stored as a constant a, and the subject distance γ +
1, and the focus compensating lens position A (γ + 1, k−1) corresponding to the zoom lens position k−1 is read from the focusing lens trajectory table T and stored as a constant b (step S19). That is, based on the focus lens locus data of the subject distance γ and the focus lens locus data one closer to the subject distance γ on the focus lens trajectory table T, the current zoom lens position k is 1 The focus compensating lens position data on the wide side is read out and stored as constants a and b.

Next, the in-focus position (the position to be followed and moved for focusing) of the focus compensating lens 15 corresponding to the zoom lens position z = k + 1 or z = k−1 is
Which is an equation corresponding to Equation 1.

[0058]

## EQU2 ## It is determined by y = (ba) α / β + a (step S20). Since the constants α and β are determined before the start of zooming as described above,
The focus lens trajectory to be followed is uniquely determined.

Next, a speed Vf at which the focus compensating lens 16 moves following the movement of the variable power lens 12 during zooming (this is referred to as a focus speed) is calculated (step S21). This focus speed Vf is a difference value (y-f: moving distance) between the focus compensating lens position y of the follow-up destination and the current focus compensating lens position f.
And the variable power lens 12 has the variable power lens positions z = k and z = k +
1 or the time required to move between z = k and z = k-1.

Next, the focus motor 23a is driven (step S22), the zoom motor 22a is driven (step S23), and the process returns to the main flow.

If it is determined in step S15 that the variable-magnification lens position is not a discrete position (boundary position) recorded in the focusing lens trajectory table T, the process proceeds to steps S16 to S16.
The process skips S21 and proceeds to step S22. That is, the update of the focus motor speed Vf is performed by the variable power lens 1
This is performed only when 2 exists at the boundary position, and the focus compensating lens 15 is moving at the focus motor speed Vf previously determined at other positions.

Here, a method of driving the focus motor 23a and the zoom motor 22a performed in steps S22 and S23 will be described.

Zoom motor 22a, focus motor 2
Drivers 22b and 23b for driving 3a are controlled by H / L direction signals S1 and S2 output from the lens control microcomputer 21 and speed signals S3 and S4 as clock frequency rotation frequency signals. Zoom motor 2
The direction signal S1 for 2a is H depending on whether the wide switch 32 or the tele switch 33 is turned on.
/ L is determined. The direction signal S2 to the focus motor 23a indicates that the focus motor speed Vf is positive /
H / L is determined depending on whether it is negative.

The drivers 22b and 23b output the direction signal S
1, the phases of the four motor excitation phases are rotated forward in accordance with S2,
Alternatively, the rotation direction and the rotation frequency of the motor are controlled by setting the rotation in the reverse direction and changing the applied voltage (or current) of the four-phase motor excitation phase according to the speed signals S3 and S4 and outputting the changed voltage. I have.

The constants α, β, γ, a, b and the variable n are, of course, stored in a work area or a register in the memory of the microcomputer 21 for lens control. There is no need to prepare a special storage area (memory).

Next, in the above flowchart, the description has been made assuming that the variable power lens 12 stops only at the boundary position. However, a case where the variable power lens 12 can stop at an arbitrary position as well as at the boundary position will be described.

In this case, in step S6 of FIG.
What is necessary is just to interpolate the focus compensating lens position by the interpolation method as shown in FIG.

That is, in FIG. 5, the vertical axis indicates the focus compensating lens position, and the horizontal axis indicates the zooming lens position. The focusing lens locus position (magnifying lens position) stored in the focusing lens locus table T is shown. , The zoom lens position is z0, ...,
zn, zk + 1,..., zn, and the focus compensating lens position at that time is a0,.
k, ak + 1, ..., an or b0, ..., bk, bk
+1, ..., bn or c0, ..., ck, ck + 1,
..., cn.

If the zoom lens position is located at a position zx not stored in the focusing lens locus table T and the focus compensating lens position is px, two focusing lens loci with respect to the zoom lens position zx The upper focus competition lens positions ax and bx are obtained by the following equations.

[0070]

Ax = (zx−zk) × (ak + 1−ak) /
(Zk + 1−zk) + ak bx = (zx−zk) × (bk + 1−bk) / (zk +
1−zk) + bk That is, the position of the zoom lens that is not stored and the position of the two stored zoom lenses sandwiching it (for example, z =
k and z = k + 1) to obtain an internal division ratio, and internally dividing a difference value between two stored focus competition lens positions sandwiching an unstored variable magnification lens position based on the internal division ratio. Thus, the focus compensating lens positions ax and bx on the two focusing lens trajectories with respect to the zooming lens positions which are not stored may be obtained, and the processing after step S7 in FIG. 3 may be performed.

[0071]

As described above, according to the lens control apparatus of the present invention, when switching from the automatic focus adjustment mode to the manual focus adjustment mode, a new focus locus is formed based on the focus locus immediately before switching. After calculating, the calculation of the in-focus trajectory is prohibited during zooming, so during zooming operation with manual focus adjustment, the in-focus state before manual focus adjustment can always be maintained, and the wrong trajectory can be maintained. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an outline of a video camera provided with a lens control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing data contents of a focusing lens trajectory table.

FIG. 3 is a flowchart illustrating lens control when zooming is performed with the AF mode turned off.

FIG. 4 is a flowchart continued from FIG. 3;

FIG. 5 is a diagram for explaining an interpolation method in the direction of the position of a variable power lens.

FIG. 6 is a diagram showing an inner focus type lens system.

FIG. 7 is a diagram showing the relationship between the position of a variable power lens for maintaining focus and the position of a focusing lens for each subject distance.

FIG. 8 is a diagram for explaining a focusing lens trajectory tracking method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 ... Magnifying lens 15 ... Focus compensating lens 21 ... Lens control microcomputer 22 ... Lens moving means 23 ... Lens moving means 32 ... Wide switch 33 ... Tele switch 34 ... Infinite switch 35 ... Close switch 36 ... AF switch T ... Focusing Lens locus table

Claims (3)

[Claims] A first lens for performing a zooming operation;
A second lens for correcting the movement of the focal plane when the first lens is moved, and lens moving means for independently moving the first lens and the second lens in parallel with the optical axis; The second position with respect to the discrete position of the first lens
The in-focus position of the first lens and the current position of the first lens and the second lens and the in-focus position stored in the in-focus position storage means are stored in advance in accordance with the discrete object distance. A subject distance specifying means for specifying a focus locus of the second lens based on the information, when the mode is switched from the automatic focusing mode to the manual focusing mode, immediately before the switching. After a new focus locus is specified based on the focus locus specified by the subject distance specifying means, and after the first lens is moved by the lens moving means to perform a zooming operation, A lens control device comprising: a control unit that prohibits updating of a focus locus by a subject distance specifying unit. 2. A first lens for performing a variable power operation,
A second lens for correcting the movement of the focal plane when the first lens is moved, and lens moving means for independently moving the first lens and the second lens in parallel with the optical axis; A focus position storage unit that previously stores trajectory information of a focus position of the second lens with respect to the first lens position in accordance with a subject distance; a current position of the first lens and the second lens; A subject distance specifying means for calculating a movement locus of the second lens based on the locus information stored in the in-focus position storage means, wherein the automatic focus adjustment mode is changed to the manual focus adjustment mode. When the switch is made, a new movement locus is calculated based on the movement locus of the second lens specified by the subject distance specifying means immediately before the switching, and the second movement is performed by the lens moving means. After starting the zooming operation by moving the lens 1,
A lens control device comprising a control unit for prohibiting a calculation of a movement locus by the subject distance specifying unit. 3. When the automatic focus adjustment mode is switched to the manual focus adjustment mode, the control means performs an internal division ratio calculation based on a movement trajectory specified immediately before the switching, and performs a new movement. 3. The lens control device according to claim 2, wherein a locus is calculated.