JPH0698236A - camera - Google Patents

Abstract

(57) [Summary] [Purpose] To enable high-speed zooming without blurring regardless of delay or lack of sharpness signal during slow shutter. [Constitution] When the charge accumulation time of the image pickup device 16 becomes long at the time of the slow shutter and the delay or lack of the sharpness signal occurs at the time of the slow shutter, the lens control microcomputer 21 causes the variable power lens 12 and the focus compensating lens 15 at the time of zooming.
Is controlled based on the focusing lens locus in the focusing lens locus table T corresponding to the subject distance specified before zooming, without using the high frequency component (sharpness signal) extracted by the filter 19.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art FIG. 8 is a block diagram of a conventionally known inner focus type lens system. As shown in FIG. 8, the inner focus type lens system 1 includes a first fixed lens 2 arranged along the optical axis in order from the subject side on the left side to the right side in FIG. To a zoom lens 3 for performing zooming, a diaphragm 4, and a second
It has a fixed lens 5 and a focus competition lens 6 having a so-called competition function that moves in parallel with the optical axis to adjust the focus and corrects when the focal plane moves due to zooming. There is. 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, photoelectrically converted, and 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 the same, the image pickup surface 7a is focused. The position of the focus compensating lens 6 for moving the lens 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 image pickup surface 7a is continuously plotted, as shown in FIG. Therefore, in order to perform zooming without blurring, during zooming, the focusing lens locus shown in FIG. 8 is selected according to the subject distance, and the focus compensating lens 6 is moved according to the selected focusing lens locus. There is a need.

In the front lens focus type lens system, an independent compensating lens is provided for the variable power lens, and the variable power lens and the competitive lens are connected by a mechanical cam ring. Therefore, for example, if a knob for manual zoom is provided on the cam ring and you try to change the focal length manually, no matter how fast you move the knob,
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 blurring.

On the other hand, in the inner focus type lens system 1, as described above, in order to carry out zooming without blurring, it is necessary to move the focus compensating lens 6 according to the locus shown in FIG. Therefore, a plurality of focusing lens locus information corresponding to the subject distance as shown in FIG. 9 is stored in the lens control microcomputer in some form (the locus itself or a function having the lens position as a variable) may be stored. A locus-following method in which a focusing lens locus is selected according to the positions of the lens 6 and the variable power lens 3 and zooming is performed while following the selected focusing lens locus is generally adopted. The details of the trajectory following method will be described later.

At this time, the positions of the variable power lens 3 and the focus competition lens 6 must be detected to some extent accurately in order to accurately control the focusing by the focus competition lens 6 and completely eliminate the blur. In particular, as is clear from FIG. 9, when the variable power lens 3 moves at a constant speed or a speed close thereto, the tilt of the focusing lens locus to be followed by the focus compensating lens 6 changes every moment due to the change of 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 makes a precise speed response from 1 Hz to several 100 Hz. It will have to be done.

In order to meet such requirements, it is becoming common to use a stepping motor as an actuator for the focus competition lens 6. 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. Because. Furthermore, when a stepping motor is used, since the step angle with respect to the step pulse number is constant, the step pulse can be used as it is as an increment type position encoder, and it is not necessary to add a special position encoder. There are also advantages.

Next, a conventional example of the above-mentioned trajectory following method for performing the zooming operation while keeping the focus in the inner focus type lens system 1 will be described with reference to FIG.

In FIG. 10, the vertical axis represents the position of the focus compensating lens 6, and the horizontal axis represents the position of the variable power lens 3. Further, z0, z1, z2, ... Z11 represent the positions of the variable power lens 3, and are represented by a0, a1, a2 ,.
1, b2, ..., B11 correspond to two different subject distances, and represent typical focusing lens loci to be followed by the focus compensating lens 6 following the movement of the variable power lens 3. The focus lens trajectory information is stored in the control microcomputer as a focus lens trajectory table.

As shown in FIG. 10, the focusing lens locus table stores only typical focusing lens loci corresponding to discrete object distances. If the user traces the stored focusing lens locus as it is, it becomes impossible to perform the zooming operation while keeping the focus. Therefore, in the case of a subject distance that is not stored, a focus lens trajectory that corresponds to a subject distance that is not stored is calculated based on the stored focus lens trajectory. P0, p1, p2, ... P1 in FIG.
1 is the calculated focusing lens locus. This p0, p
Focusing lens loci such as 1, p2, ...

[0012]

## EQU00001 ## p (n + 1) = b (n + 1) -a (n + 1) .times.p (n) -a (n) / b (n) -a (n) + a (n + 1).

According to Equation 1, for example, in FIG.
When the focus competition lens 6 is at the position p0, p0
Determines the ratio that internally divides the line segment "b0-a0", and the point that internally divides "b1-a1" according to this internal division ratio is 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 keeping the focus can be obtained.

By the way, when the variable power lens 3 moves from the telephoto to the wide direction, as is clear from FIG. 9, the inconsistent focusing lens loci are in the direction of converging, so that the above-mentioned locus-following method also works. The char can be maintained. However, in the wide-to-tele direction, since it is not known which focusing lens locus the focus compensating lens 6 located at the converging point should follow, focusing cannot be maintained by the similar locus tracking method.

Therefore, the front focus information and the rear focus information (blur) obtained during the automatic focusing operation (AF) of the contrast method (mountain climbing method) using the high frequency component (sharpness signal) of the video signal output from the image pickup device 7 are performed. A method has been proposed in which a focusing lens locus that minimizes (information) is selected, and zooming is performed while the focus compensating lens 6 is made to follow based on the focusing lens locus.

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

That is, when the AF function is in the off state, every time zooming is performed from the telephoto side capable of maintaining the focus, the focus competition for each position of z0, z1, z2, ... Z11 of the variable power lens 3 of FIG. Positions of lens 6 p0, p1, p
2, ... p11 ... (focusing lens locus) are calculated and sequentially stored in the memory in the microcomputer, and then, when zooming from the wide to the tele direction, the stored position of the focus compensating lens 6 is read out. However, the trajectory that was followed when zooming from the tele to the wide direction is traced in the opposite direction.

[0018]

However, in the above-mentioned conventional example, when zooming is performed at the slow shutter, the shutter speed becomes slower and the amount of video signal information per unit time decreases, so that the high frequency component (sharpness of the video signal is reduced. Since the extraction of the signal) is delayed or missing, the front focus information and the rear focus information cannot be correctly obtained from the sharpness signal, and the focusing lens locus to be followed cannot be correctly selected, resulting in a large blurring state.

Further, in order to correctly obtain the front focus information and the rear focus information, it is necessary to lengthen the zooming time in accordance with the rate at which the shutter speed becomes slow, and high speed zoom cannot be performed.

The present invention has been made under such circumstances, and an object thereof is to enable a high-speed zoom without blurring regardless of the delay or lack of the sharpness signal at the slow shutter. It is to be.

[0021]

In order to achieve the above object, the present invention provides a first lens for performing a zooming operation,
A second lens for correcting the movement of the focal plane when the first lens moves, and a lens moving means for independently moving the first lens and the second lens in parallel with the optical axis, An image sensor for photoelectrically converting an optical image of a subject incident through the first lens and the second lens to output a video signal, and a control unit for controlling a charge storage time of the image sensor; A camera having an extracting means for extracting a high-frequency component from a video signal output from an image sensor,
The control means controls whether or not the movement control of the first lens and the second lens by the lens moving means at the time of zooming operation is performed by using the high frequency component extracted by the extracting means. The image pickup device further includes a determination unit that determines the charge storage time according to the charge accumulation time.

[0022]

The determining means uses the high-frequency component (sharpness signal) extracted by the extracting means to control the movement of the first lens and the second lens by the lens moving means during the zooming operation. Whether or not to perform the above is determined according to the charge accumulation time of the image pickup device controlled by the control means. For example, when the charge accumulation time of the image pickup device becomes long at the time of the slow shutter and the delay or the drop of the sharpness signal occurs, the determining unit may cause the first lens, the second lens, or the like.
The lens movement control is determined so as not to use the high-frequency component (sharpness signal) extracted by the extracting means, so that it is not affected by the delay or lack of the sharpness signal at the slow shutter. , Enables high-speed zoom without blur.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment of the present invention will be described with reference to the drawings.

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

In FIG. 1, reference numeral 10 denotes an inner focus type lens system, which is similar to the conventional example described above.
In the drawing, 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 magnification lens 12 that moves in parallel with the optical axis to change the magnification, and an aperture (having a function. (Aperture / shutter) 13, second fixed lens 14, a focus competing function that moves in parallel with the optical axis to perform focus adjustment and a so-called competing function that corrects when the focal plane moves due to zooming. It has a lens 15.

The optical image of the subject by the lens system 10 is an image pickup device 1 composed of a CCD or the like.
An image is formed on the image pickup surface 16a of No. 6, photoelectrically converted, and output as a video signal. This video signal (electrical signal) is the first
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 gate circuit 39 creates a distance measuring frame for performing AF (autofocus) processing based on the high-frequency component from the filter 19 under the control of the lens control microcomputer 21, and the signal processing circuit 20 causes the AF In order to perform the processing, signal processing such as obtaining the strength or the blur width detection strength is performed on the high frequency component within the range of the distance measurement frame created by the gate circuit 39 among the high frequency components extracted by the filter 19. Do lens control microcomputer 2
Output to 1. At this time, the charge accumulation time of the image sensor 16 is controlled by the electronic shutter 40 under the command of the lens control microcomputer 21.

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

Then, a movement command signal (direction signal s1, s2, speed signal s) output from the lens control microcomputer 21.
The driving energy is output from the drivers 22b and 23b according to (3, s4) and supplied to the zoom motor 22a and the focus motor 23a, respectively, and the output shafts 22c and 23c
As a result of rotation, the variable magnification lens 12 and the focus compensating lens 15 move integrally with the racks 22d and 23d in parallel with the optical axis (directions of arrows A and B in the figure).

The positions of the variable power lens 12 and the focus competition lens 15 are lens position detecting means 24 and 25, respectively.
Detected by. The lens position detecting means 24, 25 are
Photosensors 24a and 25a and light shielding plates 24b and 25b
The photosensors 24a and 25a are composed of a light emitting portion and a light receiving portion (not shown), and the light shielding plate 24b,
Reference numerals 25b are fixed to the variable power lens 12 and the focus competition 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 with them, and the photosensors 24a and
When the optical path between the light emitting portion and the light receiving portion of 25a is blocked, the output signal of the light receiving portion is at a low level, and when not blocked, it is at a high level.

Therefore, with the position where the output signal of the light receiving section changes as the reference position, it is possible to detect whether or not the variable power lens 12 and the focus compensating lens 15 are present at 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 diaphragm 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 this level is not a constant level (appropriate exposure amount), generates an aperture amount control signal for making the level constant. The aperture amount control signal is amplified by the second amplifier 28 and output to the driver 26, and the driver 26 drives the aperture 13 so as to obtain an appropriate exposure amount.

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

In the lens control microcomputer 21, the wide switch 32 for moving the variable power lens 12 in the wide direction and the tele switch 33, and the focus compensating lens 15 are moved in the infinity direction and the close-up direction, respectively. Infinity switch 34 for close, close switch 3
5. An AF switch 36 for setting the AF mode is connected. Each of these switches and the lens control microcomputer 21
A power source 38 is connected to the connection line with the via a pull-up resistor 37.

The lens control microcomputer 21 is preset with a focusing lens locus table T as shown in FIG. 2, which is a table of the focusing lens locus contents of FIG. That is, the focusing lens locus table T of FIG.
Focus compensating lens 1 corresponding to 2 discrete positions
5 is a table in which the in-focus positions of No. 5 are recorded for each object distance, and n (0, 1, ..., K, ...) In the column direction (horizontal direction in the figure)
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, and the columns and rows are The position of the discrete variable power lens 12 and the in-focus position of the focus compensating lens 15 corresponding to the subject distance are recorded at the intersection position of. Note that the subject distance becomes shorter as it moves to the right in the figure, "0" indicates infinity, and "m" indicates the nearest 1 cm. Further, at the variable power lens position, the zoom area becomes wider as it goes downward in the figure, and “0” is displayed.
Indicates the tele end, and “l” indicates the wide end. Then, the focus position of the focus competition lens 15, for example, A
0k indicates the focus position of the focus compensating lens 15 when the subject distance is "0" and the position of the variable power lens 12 is "k".

When performing zooming from wide to tele in the AF mode other than slow shutter, the lens control microcomputer 21 utilizes the front and rear pin information to focus lenses in the focus lens locus table T. The focus compensating lens 15 is made to follow while sequentially selecting loci (while updating the subject distance and locus parameters) or calculating the focusing lens position based on the focusing lens locus. Perform zooming. On the other hand, when performing zooming from wide to tele during slow shutter, the focus compensating lens 15 is made to follow based on the subject distance and trajectory parameters specified when a manual focusing operation is performed before zooming.

Next, lens control for zooming will be described with reference to the flow charts of FIGS. In addition, the flow of FIGS. 3 and 4 is made into a subroutine,
Before this flow is executed, the AF mode processing by the contrast method (mountain climbing method) that controls the automatic focus adjustment according to the focus voltage (sharpness of the image signal) is executed. Further, in the flow of FIG. 3 and FIG.
It is premised that the lens is stopped only at the discrete positions recorded in the focusing lens trajectory table T of FIG.

The lens control microcomputer 21 first determines whether or not the wide switch 32 and the tele switch 33 are on / off to determine whether or not zooming is in progress (step S1). As a result, either one of the wide switch 32 and the tele switch 33 is turned on, and if zooming is in progress, the process proceeds to step S6 described later. On the other hand, if neither the wide switch 32 nor the tele switch 33 is turned on and zooming is not in progress, the counter C is set to "3" (step S2), and it is determined whether the AF switch 36 is on or off. , It is determined whether or not the AF mode is set (step S3). As a result, if the AF switch 36 is turned on and the AF mode is set,
The process proceeds to step S10 described below. When the AF mode is set in this way, focusing control is performed by an AF mode processing routine (not shown). On the other hand, AF
If the switch 36 is turned off and the AF mode is not set, it means that the manual focus mode is currently set, and whether the manual focus mode has been set by switching from the AF mode or has been set before. It is determined whether the manual focusing mode has been set all the time (step S4). As a result, if the manual focus mode has been set for a long time, it is determined whether or not the power focus state is set by determining whether the infinite switch 34 and the close-up switch 35 are on or off (step S5). As a result, if either the infinite switch 34 or the closest switch 35 is turned on and the power focus state is set, it means that the focus control is manually performed. In this case, the process proceeds to step S10. On the other hand, if neither the infinite switch 34 nor the close-up switch 35 is turned on and the power focus state is not set, the process after step S10 is performed after the focus control is manually performed, and the process returns to the main flow.

If the AF mode is switched to the manual focusing mode in step S4, it means that the focusing control has already been automatically performed in the AF mode before the switching, and thus step S5 is skipped. Then, the process proceeds to step S10.

If it is determined in step S1 that zooming is in progress, whether or not the shutter speed selected by a switch (not shown) is higher than a predetermined value S, in other words, the electronic shutter 40 controls the shutter speed. It is determined whether or not the charge accumulation time of the image pickup device 16 that should be used is longer than the predetermined value S (step S6). In this case, for example, if the shutter speed as shown in FIG.
A shutter speed of / 30 (sec) is set to a predetermined value S.

When it is determined in step S6 that the shutter speed is larger than the predetermined value S = 1/30 (sec), that is, when the charge accumulation time of the image pickup device 16 is longer than 1/30 (sec) in the slow shutter. Judges whether or not the wide switch 32 is turned on, and zooming in the wide direction from the tele is instructed (step S7). As a result, if zooming in the wide direction from the tele is instructed, it is determined whether or not the count value of the counter C has become "0" (step S8). As a result, if the count value of the counter C is not "0", the count value of the counter C is decremented by 1 (step S9), and the process proceeds to step S10.

In steps S10 to S19, the focus lens locus to be moved by the focus compensating lens 15 is stored in accordance with the movement of the variable power lens 12 during zooming.
This is a routine for specifying the subject distance and the internal division ratio in the mathematical expression 1. As will be clear from the above description, the AF mode when the zooming is stopped,
This is a case where the manual focusing mode when switching from the AF mode and the power focus are performed. Also, as described later, the shutter speed is a predetermined value S = 1/3.
If it is smaller than 0 (sec) and the charge accumulation time of the image sensor 16 is shorter than 1/30 (sec), the step S is performed even during zooming in the wide-to-tele direction during AF.
It goes through the routine of 10 to S19. Further, when the shutter speed is larger than the predetermined value S = 1/30 (sec) and the charge storage time of the image pickup device 16 is longer than 1/30 (sec), the counter is displayed just before zooming from the telephoto to the wide direction. While counting 3 by C, the routine of steps S10 to S19 is passed. In other words, at slow shutter speed, the focusing lens locus traced by zooming in the wide direction from the telephoto side will be traced in the opposite direction by zooming in the wide angle direction to the telephoto direction. Will be updated before.

That is, in step S10, an initial value "0" is set to the variable n for the object distance. Next, A
(N, k), A (n + 1, k), that is, the subject distance n
Then, the current zoom lens position k and the focus compensating lens position corresponding to the subject distance n + 1 and the current zoom lens position k are read from the focusing lens trajectory table T (step S11).

Then, it is determined whether or not the current focus compensating lens position f is A (n, k) or more (step S12). Here, as shown in FIG. 9, at a predetermined zoom lens position, the focus competition lens position f
Indicates that the subject distance increases as the subject distance approaches, so step S12 means that it is determined whether or not the current focus competition lens position f is closer to the subject distance n. There is. At step S12, the current focus competition lens position f is the subject distance n.
When it is determined that the current focus competition lens position f is smaller than A (n + 1, k), that is, the current focus competition lens position f is determined.
Is determined to be on the infinity side of the subject distance n + 1 (step S13). 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. In this case, f−A (n, k) is calculated, and the calculation result is stored as a constant α (step S1).
4). Then, A (n + 1, k) -A (n, k) is calculated, and the calculation result is stored as a constant β (step S
15). Next, the current content of the variable n (subject distance) is stored as a constant γ (step S16), and the process returns to the main flow.

If it is determined in step S12 that the current focus competition lens position f is on the infinity side of the subject distance n, the current focus competition lens position f is on the subject distance of ultra-infinity. In this case, “0” is stored as the constant α for the subject distance (step S17), and the process proceeds to step S15.

When it is determined in step S13 that the current focus compensating lens position f is closer to the subject distance n + 1, the content of the variable n for the subject distance is
It is determined whether or not the distance is the closest m on the focusing lens trajectory table T or more (step S18). as a result,
If it is not more than m, the content of the variable n is incremented by 1 (step S19), and the process returns to step S11 to check which subject distance the current focus compensating lens position f exists as described above. .

On the other hand, if the content of the variable n for the subject distance is equal to or greater than m, it means that the current focus compensating lens position f is at the subject distance of the super close distance. As in the case of being in the distance, “0” is stored as the constant α for the object distance (step S17),
It proceeds to step S15. These constants α, β, γ are used as trajectory tracking parameters, as will be described later.

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

After the object distance and the trajectory tracking parameter are specified, the focus motor 23a is moved to the focus speed V.
It is driven at f (step S31), and the process returns to the main flow. Note that this focus speed Vf is
The F mode processing routine calculates the focus speed during AF and during manual operation and stores it as a constant Vf. Further, in this AF mode processing routine, the correction speed VAF for correcting the focus plane shift is calculated from the front focus and rear focus information during zooming in the wide-to-tele direction during AF, and the tele-to-wide range during slow shutter is calculated. Before the direction zooming is started, that is, while the count C is counting down from "3" to "0", the focus speed Vf is set to 0 and the focus compensating lens 15 is used.
Has stopped moving.

During zooming, when it is determined in step S6 that the shutter speed is greater than the predetermined value S = 1/30 (sec), and when it is determined in step S7 that the zooming is from wide to tele direction. , And when it is determined in step S8 that the counter C has finished counting 3, the process proceeds to step S20.

In step S20, it is determined whether or not the current zoom lens position z = k is a discrete position (boundary position) recorded in the focusing lens locus table T. In this flow, as described above, it is premised that the variable power lens 12 is stopped only at the boundary position. Therefore, at the start of zooming, the variable power lens 12 is at the boundary position, and the flow advances to step S21 to set the wide angle. To determine whether or not zooming in the tele direction is being performed. As a result, during zooming in the wide-to-tele direction, the subject 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 trajectory table T and set as a constant a. Remember, 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 S22). That is, on the focusing lens trajectory table T,
From the focusing lens locus data for the subject distance γ and the focusing lens locus data for the one closest to the subject distance γ, the telephoto side focus compensating lens position data is read one from the current zoom lens position k. , Constants a and b are stored. On the other hand, during zooming from the telephoto to the wide direction, the subject distance γ and the zoom lens position k−
Focus compensating lens position A corresponding to 1 (γ, k-
1) is read from the focusing lens locus table T and stored as a constant a, and the focus compensating lens position A (γ +) corresponding to the subject distance γ + 1 and the variable magnification lens position k−1.
(1, k-1) is read from the focusing lens trajectory table T and stored as a constant b (step S23). That is, on the focusing lens locus table T, from the focusing lens locus data of the subject distance γ and the focusing lens locus data one closer to the subject distance γ, 1 from the current variable magnification lens position k, respectively. 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 follow and move for in-focus) y of the focus compensating lens 15 corresponding to the zoom lens position z = k + 1 or z = k-1 is
It is a formula corresponding to Formula 1,

[0053]

## EQU00002 ## y = (b-a) .alpha ./. Beta. + A, which is a difference value (y- between the focus compensating lens position y of the tracking destination and the current focus compensating lens position f.
f) That is, zooming is performed by the moving distance of the focus compensating lens 15 and the time required for the variable power lens 12 to move between variable power lens positions of z = k and z = k + 1 or z = k-1. The speed (focus competition speed) Vcp when the focus competition lens 15 moves is calculated by following the movement of the variable power lens 12 (step S).
24). Since the constants α and β are determined before the start of zooming as described above, the following focusing lens locus is uniquely determined.

Next, the shutter speed is a predetermined value S = 1.
It is determined whether or not it is larger than / 30 (sec) (step S25). As a result, the predetermined value S = 1/30 (sec)
If smaller, it is determined whether or not zooming in the wide-to-tele direction is being performed in the AF mode (step S2).
6). As a result, if zooming in the wide-to-tele direction is being performed in the AF mode, that is, zooming in the wide-to-tele direction is performed in the AF modes other than the slow shutter in which the shutter speed is equal to or lower than the predetermined value S = 1/30 (sec). When performing, the charge accumulation time of the image sensor 16 is ⅓
It is shorter than 0 (sec), there is no delay or omission of the sharpness signal, and the front focus information and the rear focus information can be correctly obtained from the sharpness signal. Therefore, tracking is performed while selecting the focusing lens locus to be followed during zooming. Therefore, the process proceeds to step S30 through steps S28 and S29.

That is, in step S28, the above-described correction speed VAF obtained from the front focus and rear focus information determined based on the change in the sharpness signal is read out, and the focus speed Vf = Vcp + VAF is set. Then, the above step S11
By executing the routines (1) to (19), the constants α, β, and γ are obtained again from the current zoom lens position and focus compensating lens position (step S29). Constants α, β,
After recalculating γ, the zoom motor 22a is driven (step S30), the focus motor 23a is driven (step S31), and the process returns to the main flow.

When it is determined in step S25 that the shutter speed is a slow shutter speed larger than the predetermined value S = 1/30 (sec), steps S28 and S28 are performed.
In order to follow up only based on the focusing lens locus corresponding to the object distance specified before the start of zooming, without performing the processing of 29, that is, without following the focusing lens locus during zooming, The focus competition speed Vcp calculated in step S24 is set to the focus speed Vf.
(Step S27), the process proceeds to step S30 and thereafter.

As described above, the charge accumulation time of the image pickup device 16 is long and the video signal amount per unit time is decreased, so that the sharpness signal is delayed or missing. At the time of slow shutter where information cannot be obtained correctly, the sharpness signal is not used, and the focus compensating lens 15 is made to follow only the focusing lens locus corresponding to the subject distance specified before the start of zooming. Can be avoided. Further, since it is not necessary to lengthen the zooming time according to the rate at which the shutter speed becomes slow, it is possible to perform high speed zooming.

If it is determined in step S205 that the zoom lens position is not the discrete position (boundary position) recorded in the focusing lens trajectory table T, step S2.
1 to S29 are skipped and the process proceeds to step S30 and thereafter.
That is, the focus speed Vf is updated during zooming only when the variable power lens 12 is present at the boundary position, and the focus compensating lens 15 moves at the previously determined focus speed Vf at other positions. There is.

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 rotation frequency signals of a clock waveform. 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. Further, H / L of the direction signal S2 to the focus motor 23a is determined depending on whether the focus speed Vf is positive or negative.

The drivers 22b and 23b use the direction signal S
1, the forward phase of the motor excitation phase of 4 phases according to S2,
Alternatively, the rotation direction and the rotation frequency of the motor are controlled by setting the reverse rotation and outputting while changing the applied voltage (or current) of the four-phase motor excitation phases according to the speed signals S3 and S4. There is.

Next, in the above flow chart, the variable power lens 12 is described to stop only at the boundary position, but a case where the variable power lens 12 can be stopped not only at the boundary position but also at an arbitrary position will be described.

In this case, in step S11 of FIG. 4, the focus compensating lens position may be interpolated by the interpolation method shown in FIG.

That is, in FIG. 7, the vertical axis represents the focus compensating lens position and the horizontal axis represents the variable magnification lens position, respectively. The focusing lens locus position (variable magnification lens position) stored in the focusing lens locus table T is shown. The focus compensating lens position) for the zoom lens position is z0, ...,
zn, zk + 1, ..., Zn, and the focus compensating lens position at that time is a0, ..., ak, depending on the object distance.
ak + 1, ..., an, or b0, ..., bk, bk + 1,
, Bn, or c0, ..., Ck, ck + 1, ..., Cn.

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

[0066]

## EQU00003 ## ax = (zx-zk) .times. (Ak + 1-ak) / (zk + 1-zk) + ak bx = (zx-zk) .times. (Bk + 1-bk) / (zk + 1-zk) + bk That is, it is not stored. The variable power lens position and the two stored variable power lens positions that sandwich the variable power lens position (for example, z =
k and z = k + 1) to obtain an internal division ratio, and based on the internal division ratio, internally divide a difference value between two stored focus compensating lens positions that sandwich an unstored variable magnification lens position. Thus, the focus compensating lens positions ax and bx on the two focusing lens loci with respect to the variable magnification lens position which are not stored may be obtained, and the processing from step S12 of FIG. 4 may be performed.

[0067]

As described in detail above, according to the camera of the present invention, movement control of the zoom lens and the focus compensating lens during zooming is performed by controlling the high frequency component (sharpness signal) of the extracted video signal. By selecting whether or not to use it according to the charge accumulation time of the image sensor, that is, the shutter speed, high-speed zoom without blurring is not affected by the delay or lack of the sharpness signal at the slow shutter. It will be possible.

[Brief description of drawings]

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

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

FIG. 3 is a flowchart showing lens control when zooming is performed.

FIG. 4 is a flowchart continued from FIG.

FIG. 5 is a continuation of the flowchart of FIG.

FIG. 6 is a diagram showing an example of selectable shutter speeds.

FIG. 7 is a diagram for explaining an interpolation method in a position of a variable power lens.

FIG. 8 is a diagram showing an inner focus type lens system.

FIG. 9 is a diagram showing a relationship between a zoom lens position and a focus competition lens position for maintaining focus for each object distance.

FIG. 10 is a diagram for explaining a focusing lens trajectory tracking method.

[Explanation of symbols]

 12 variable magnification lens 15 focus compensating lens 16 image sensor 19 filter 20 signal processing circuit 21 lens control microcomputer 22 lens moving means 23 lens moving means 22a zoom motor 23a focus motor 32 wide switch 33 teleswitch 34 infinite switch 35 close-up switch 36 AF Switch 39 Gate circuit 40 Electronic shutter T Focusing lens trajectory table

Claims (1)

[Claims] 1. A first lens for performing a zooming operation,
A second lens for correcting the movement of the focal plane when the first lens moves, and a lens moving means for independently moving the first lens and the second lens in parallel with the optical axis, An image sensor for photoelectrically converting an optical image of a subject incident through the first lens and the second lens to output a video signal, and a control unit for controlling a charge storage time of the image sensor; A camera having extraction means for extracting a high-frequency component from a video signal output from an image sensor, wherein movement control of the first lens and the second lens by the lens movement means at the time of zooming is performed by A camera provided with a deciding means for deciding whether or not to use the high frequency component extracted by the extracting means according to the charge accumulation time of the image pickup device controlled by the control means.