JP2774832B2 - Varifocal lens controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a varifocal lens control device, and more particularly, to a variable power lens group and a focusing lens group arranged on the same optical axis. The present invention relates to a varifocal lens control device in a variable power optical system, in which the relationship between the subject distance and the amount of extension of the focusing lens unit in the optical axis direction differs at magnification positions within a variable power range.

[Conventional technology]

The zoom lens has no image position shift (so-called focus shift or focus shift) even when the zooming operation is performed. Therefore, there is no need to adjust the focus for each zooming operation and the operability is good. Since the open aperture F number is dark, some skill is required for focus adjustment (focusing operation) using, for example, a single-lens reflex finder.

In recent years, the use of AF in cameras has been advanced, and by solving this problem, the original mobility of the zoom lens can be demonstrated, and the operator (user) must concentrate his attention only on deciding the composition according to the drawing intention. Operability has been greatly improved.

Generally, focusing (focusing operation) of a zoom lens
Is performed by moving a focusing lens group provided in a part of the variable power optical system. The zoom lens has an advantage that the moving amount of the focusing lens group is substantially the same for the same object distance in the entire zoom range (hereinafter, this is referred to as “equivalent movement”). It is only necessary to attach a distance scale to the moving member (distance ring) of the focusing lens group, and to attach an index to a fixed ring disposed adjacent thereto.
There is an advantage that it is not necessary to change the subject distance scale according to zooming.

However, although it depends on the lens configuration of the variable power optical system, in the case of the inner focusing type and the rear focusing type zoom lens, when the optical design is performed under the condition that the above-described equal distance movement is realized, the lens configuration becomes complicated. In addition, there is a problem that the moving amount (extending amount) of the focusing lens unit on the wide-angle side becomes unnecessarily large.

As described above, the operability of the zoom lens has been improved by the combination with the AF function. However, the problem that the zoom lens cannot escape from the above-described condition of the same amount of movement still remains. Was.

Accordingly, the present applicant has proposed an invention relating to a varifocal lens control device capable of solving the above-described problems (hereinafter, referred to as "prior invention") to JP-A-63-182620.

That is, the above-mentioned prior invention provides a variable power optical system including a variable power lens group and a focusing lens group disposed on the same optical axis, and adjusts the focusing lens group to a subject distance from a close distance to an infinity distance. After setting the focal position between the closest position on the optical axis to the infinity position, the focal length of the entire system of the variable power optical system is set to the shortest focal length and the longest focal length by the variable power lens group. A varifocal lens that causes an image forming position shift for the same subject as a result of updating from an arbitrary first focal length to a second focal length between Focusing lens group position detecting means for detecting the position of the focusing lens group on the optical axis, and receiving the output of the focal length detecting means from the infinity position of the focusing lens group at the focal length. To the nearest position Maximum feeding amount calculating means for calculating the displacement amount; proportional constant calculating means for receiving the outputs of the maximum feeding amount calculating means and the focusing lens group position detecting means and calculating the ratio of these outputs; Receiving the outputs of the calculating means, the maximum extension amount calculating means, and the focusing lens group position detecting means, and calculating, as a correction amount, an image forming position shift amount from the in-focus position caused by updating the focal length of the entire system. Focusing correction calculating means, focusing drive means for driving the focusing lens group, movement amount monitoring means for generating a signal corresponding to the movement amount of the focusing lens group, Focusing correction calculating means, variable power driving means for driving the variable power lens group, and variable power control means for controlling the variable power driving means in response to a start signal from a separately provided starting means; An imaging position deviation caused by the focal length of the updating of the variable power optical system is configured to automatically correct.

[Problems to be solved by the invention]

According to the prior application invention configured as described above, the lens optical system itself has a very simple configuration, is small, lightweight, and inexpensive, and the entire lens control device is similarly compact, lightweight, and inexpensive. Even if the variable power lens group is moved from an arbitrary first focal length to a second focal length and the focal length of the entire system is updated, the image forming position peculiar to the varifocal lens is corrected, and the focus state is changed. Therefore, it is possible to obtain a zoom lens which is substantially equivalent to a zoom lens in terms of usability.

However, the varifocal lens does not change the in-focus position at the infinity position (） position) with respect to the change of the entire system focal length from the shortest focal length to the longest focal length. When the position is configured to change away from the infinity position, for example, an attempt is made to perform focus correction control on the focusing lens group while performing a magnification operation from the long focal length side to the short focal length side of the variable power lens group. When trying to perform focus correction control of the focusing lens group while performing a magnification change operation from the short focus side to the long focus side, on the contrary, in the focus correction control diagram of the varifocal lens shown in FIG. (B), (c)
However, there is a problem that a delay in following the focus correction occurs as shown in FIG.

That is, in the case where the zooming operation and the focus correction operation are performed simultaneously, the ideal focus correction control diagram is a diagram shown by a curve a. , The curve b when zooming from the tele side (telephoto side focal length) to the wide side (wide angle side focal length), and the curve b when zooming from the wide side to the tele side compared to the curve a. As shown in the curve c, that is, as if a hysteresis loop was drawn, there was a problem that a delay in focusing correction follow-up occurred for the curve a.

Further, in order to appropriately perform the focus correction control without the delay of the focus correction follow-up as described above, the focus correction control time must be corrected in advance while considering the focus correction control time. As shown in FIG. 4, since it greatly changes depending on the drive voltage of the motor and the focus correction amount,
Until now, such measures have not been reached.

In the conventional case, the cause of the delay of the focus correction control is that the focus correction calculation calculates the focus shift at the current position of the variable power lens group and performs the correction control on the focus lens group. This is because even during the focus correction control, the variable power lens group is driven to change the magnification, thereby causing a focus shift.

The present invention has been made in view of the above circumstances, and an object of the present invention is to drive the focusing lens group once and then set the entire system focal length to an arbitrary value between the shortest focal length and the longest focal length. Can be automatically corrected in the case where the first focal length is updated from the first focal length to the second focal length, and the variable power lens group can be automatically corrected especially during the correction control operation. It is an object of the present invention to provide a vari-focal lens control device which can improve the follow-up performance by correcting the in-focus deviation accompanying the driving of the lens, thereby improving the operability.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a variable power optical system including a variable power lens group and a focusing lens group disposed on the same optical axis, and includes a subject distance and an optical axis of the focusing lens group. In the varifocal lens, the relationship with the amount of extension in the direction is different at a magnification position within the variable power range, focus driving means for driving the focusing lens group, variable power driving means for driving the variable magnification lens group, Focusing lens military value detection means for detecting a position on the optical axis of the focusing lens group; and a variable power lens group position for detecting a position on the optical axis corresponding to the focal length of the variable power lens group. Detecting means for receiving the focusing lens group position information and the variable power lens group position information output from the focusing lens group position detecting means and the variable power lens group position detecting means, respectively; No imaging position caused by movement And it calculates the correction amount,
A focus correction time for performing the focus correction on the correction amount by the focusing lens group is predicted and calculated, and a focus shift correction amount in consideration of the zoom movement amount of the zoom lens group during the focus correction time is calculated. A focus correction amount calculating means for calculating and calculating a focus correction control amount obtained by adding the correction amount and the focus shift correction amount; and receiving the information on the focus correction control amount, and Focusing correction control means for controlling the focus driving means so as to drive the focus lens group to a focus position at the focal length at the time, The image forming apparatus according to the present invention is characterized in that the image forming position shift due to the updating is automatically controlled while performing the zooming movement of the zooming lens group.

(Operation)

The focus correction amount calculating means of the varifocal lens control device configured as described above includes the focusing lens group position information and the zooming power output from the focusing lens group position detecting means and the zooming lens group position detecting means, respectively. Receiving the lens group position information, calculating the imaging position shift caused by the zooming movement of the zooming lens group as a correction amount, and focusing the correction amount by the focusing lens group. The correction time is estimated and calculated, the focus shift correction amount is calculated in consideration of the zoom movement amount of the zoom lens group during the focus correction time, and the correction amount and the focus shift correction amount are added. A focus correction control amount is calculated. Then, the focus correction control means, which has received the data of the focus correction control amount from the focus correction amount calculation means, drives the focus lens group to the focus position at the focal length at the time when the focus correction time has elapsed. The focusing driving means is controlled as described above.

Therefore, the focus shift caused by the delay of focusing correction follow-up of the focusing lens group accompanying the zooming movement of the zooming lens group as in the related art can be prevented, and during the zooming of the zooming lens group. Even if it does, ideal varifocal control can be achieved.

In addition, since the follow-up performance of the focusing lens group during focus correction is remarkably improved, unnecessary operations can be avoided, so that the lens can be quickly driven and the driving energy is saved, and operability is generally improved. Is improved.

〔Example〕

Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

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

In FIG. 1, reference numeral 1 denotes an optical axis of a variable power optical system, and 2 denotes a varifocal lens which is disposed on the optical axis 1 so as to be movable along the optical axis 1 and constitutes the variable power optical system. In the variable power lens group, reference numerals 2a, 2b, 2c, 2d, and 2e denote a first group lens, a second group lens,
A group lens, a fourth group lens, and a fifth group lens. The third group lens 2c includes the first group and the second group lenses 2a and 2b.
The zoom lens group 2 is constituted by the fifth to second lens groups 2e, and the focusing lens group 3 is constituted by the first lens group 2a and the second lens group 2b. F is the film surface.

Reference numeral 4 denotes a focal length from the telephoto side focal length (hereinafter simply referred to as “tele side”) as the longest focal length to the wide angle side focal length (hereinafter simply abbreviated as “wide side”) as the shortest focal length. zooming driving unit consisting of zooming motor M _Z and an unillustrated mechanism as zooming driving means for driving the zooming lens group 2 to be set to any of the focal length of between 5
Drives the first lens unit 2a and the second lens unit 2b to a focus position from an infinity position (∽ position) on the optical axis 1 corresponding to a subject distance from infinity to a close position to a close position (details) the focus drive unit consisting of the focus motor M _F and a mechanism (not shown) of the optical axis direction allowed to move) focusing drive means while maintaining the distance between the first lens 2a and the second group lens 2b constant It is.

Reference numerals 6 and 7 denote a focusing lens group 3, that is, a focusing counter group driven by the focus driving unit 5 together with the first group lens 2a and the second group lens 2b and a focusing lens group as a focusing lens group position detecting means. The focus counter 6 generates a pulse proportional to the number of rotations from a photo interrupter 6b when the slit disk 6a is rotationally driven, and focuses on the position. The FPM 7 detects the amount of movement of the lens group 3 on the optical axis 1. The FPM 7 converts a voltage proportional to the position of the focusing lens group 3 on the optical axis into focus position information as focusing lens group position information. Output as Sx. Numeral 8 denotes a variable power lens group position detecting means which is driven by the variable power drive unit 4 together with the variable power lens unit 2 and outputs a voltage proportional to the focal length of the entire system as focal length information Zp as variable power lens group position information. Is a variable magnification lens group position detector (hereinafter abbreviated as “ZPM”).

Reference numeral 9 denotes a maximum feed for receiving the focal length information Zp, subjecting the focal length information Zp to A / D conversion, and calculating a movement amount (that is, a feed amount) Fpx of the focal length information from the ∽ position to the closest position in the focal length information Zp. The amount calculating unit 10 includes an output Fpx of the maximum feeding amount calculating unit 9 and an output S of the FPM 7 as focus position information.
x is an A / D conversion of the output Sx, calculates a ratio between them, and outputs a proportional constant Cfp.

11a receives the above three outputs Fpx, Cfp, and Sx and calculates a correction amount (driving amount) Dfp for correcting (focusing) an imaging position shift caused by the variable power movement of the variable power lens group 2. When Dfp.gtoreq.Dmax as compared with a predetermined limited drive amount Dmax, the focusing correction calculation unit outputs the Dmax.

Numeral 11b experimentally and empirically predicts and calculates a focus correction time in which the correction amount Dfp is corrected by the focus lens group 3, and changes the magnification of the zoom lens group 2 during the focus correction time. A focus shift correction amount of the focusing lens group 3 in consideration of the movement amount is calculated, and a focus correction control amount Dfp 'obtained by adding the above-mentioned correction amount Dfp and the focus shift correction amount is calculated, and is shown in FIG. Is a focus correction amount calculation unit provided to correct the movement of the focusing lens group 3 on a focus correction line to be described later.
11b and the above-mentioned focusing correction calculating section 11a constitute a focusing correction amount calculating means. The focus correction amount calculation unit 11b will be described later with reference to FIG.

Reference numeral 12 denotes an output Dfc of the focus counter 6 and a drive control unit 12a.
Focus correction control for controlling the focus driving unit 5 in response to the prohibition signal (H) output from the controller and the output Dfcd corresponding to the focus correction control amount Dfp 'shown in FIG. It is a focus control unit as a means.

12a is a limit signal (Lm), wide signal (WS
W), a tele-signal (TSW), a switching signal (CX), and a focus correction control amount (Dfp ′). .

Reference numerals 13 to 14 constitute a starter, and reference numerals 13 and 14 denote operation switches and change-over switches which are externally operable push button switches, of which 13a is a magnification up contact (hereinafter simply referred to as "up contact"), 13b Is a magnification down contact (hereinafter simply referred to as “down contact”). Reference numeral 14 outputs a switching signal (CX) for instructing a focusing operation in an OFF state and instructing a magnification operation in an ON state. When the changeover switch 14 is instructing the focusing operation, if the operation switch 13 is on the up contact 13a side, the tele signal (TSW) output from the up contact 13a indicates the movement to the close side, and the down contact 1
When the switch is on the 3b side, the wide signal (WSW) output from the down switch 13b indicates movement to the ∽ side.

Reference numeral 15 denotes a lens position determining unit serving as a lens position determining unit that receives the above-mentioned feeding amount (Fpx) and the focus position information (Sx) and outputs a limit signal (Lm) when the focusing lens group 3 is within the prohibited area. is there.

Reference numeral 16 denotes a variable power control unit that receives the start signal STR and the motor speed signal Zmv and controls the variable power drive unit 4, and 16 a generates an electric power at the variable power motor Mz when the variable power control unit 16 drives the variable power motor Mz. A back electromotive voltage detector detects the back electromotive voltage and outputs it as a motor speed signal (Zmv).

Reference numeral 17 denotes a photographing distance as a photographing distance detecting means which measures a distance to a subject, outputs distance measurement data (AF) corresponding to the photographing distance, and outputs a display signal (Dot) in response to a proportional constant (Cfp). It is a detection unit.

Reference numeral 18 denotes a display unit for receiving the display signal (Dot), 18a denotes an index unit including 12 display dots, and 18b and 18c denote the index unit.
Numerical part corresponding to 18a and having units of "meter" and "foot", respectively. In addition, the input / output relationship of each part shows only the main signal.

FIG. 2 is a graph showing the characteristics of the varifocal lens shown in FIG. 1, in which the total focal length f to be set and the objects of the focusing lens group 3 (the first group lens 2a and the second group lens 2b). The extension amount (movement amount) corresponding to the distance D is shown for each representative object distance D, the vertical axis indicates the change in the focal length f of the entire system, and the horizontal axis indicates the focus based on the in-focus position with respect to infinity. The amount of extension of the lens group 3 is shown. In this example,
The tele position is f = 135mm and the wide position is f = 35m
m.

In FIG. 2, reference numerals 19 to 24 denote focusing curves, in which the subject distance D on the left side in Expression (1) is ∽, 6.0 m, 3.0 m,
This shows the change in the amount of extension of the focusing lens unit 3 from the infinity position to the in-focus position with respect to the change in the focal length information Zp when the distance is 2.0 m, 1.5 m, and 1.2 m. That is, the subject distance D
Can be obtained from the focal length information Zp and the focus position information Sx by using the following equation, where C ₀ , C ₁ , and C ₂ are set constants determined at the time of design.

D = (C ₀ · Zp + C ₁ ) · Sx + C ₂ (1) Accordingly, the focusing curve 24 shown in FIG. 2 is the closest focusing curve having the maximum extension amount, and particularly the closest focusing curve 24. Fpx
And

 The operation of the present embodiment configured as described above will be described.

First, the magnification operation and the focusing operation will be described. here,
It is assumed that the changeover switch 14 in FIG. 1 is in an OFF (open) state and the operation switch 13 is in a neutral state. The drive control unit 12a checks a switching signal (CX) from the changeover switch 14. In this case, since the changeover switch 14 is OFF, the drive control unit 12a
Is determined to be a focusing operation. This drive control unit 12a
The tele signal (TSW) and the wide signal (WSW) are checked. In this case, since the operation switch 13 is in the neutral state and no signal is output, the prohibition signal (H) is output, and the focus control receiving the signal is performed. part 12 apply the electromagnetic brake to the focus motor M _F.

Now, assuming that the operation switch 13 is closed to the up contact 13a, the drive control unit 12a detects the tele signal (TSW) and checks the limit signal (Lm). on the other hand,
The lens position determination unit 15 receives the output (Fpx) from the maximum extension amount calculation unit 9 and determines whether or not the focusing lens group 3 is within the limit zone on the close side or the ∽ side. Outputs the signal (Lm). If there is no signal, stops outputting the limit signal (Lm). Assuming that the focusing lens group 3 is within the close limit band, the limit signal (Lm) is output,
This is detected by the drive control unit 12a, and the inhibition signal (H) is output.

Now, if the focusing lens group 3 is located at a position outside the restricted zone, the drive control unit 12a stops outputting the prohibition signal (H) and outputs a correction drive signal (Dfcd). The correction drive signal (Dfcd) simply controls the drive direction and stop]. In response to this, the focus control unit 12
Drives the focusing lens group 3 in the closest direction.

Now, the case where the operation switch 13 is closed to the down contact 13b side is the same, except that the driving direction is different.

Next, the operation when the changeover switch 14 is ON, that is, the variable power operation will be described. The operation switch 13 is set to neutral for the time being.

First, as described above, the drive control unit 12a outputs the wide signal (WS
Check W) and Telesignal (TSW). Since the operation switch 13 is neutral, the variable power control unit 16 applies an electromagnetic brake to the variable power motor Mz.

Here, assuming that the operation switch 13 is closed to the up contact 13a side, the drive control unit 12a determines that the direction is the telephoto direction, that is, the magnification increasing direction by input of the telesignal (TSW), and outputs the focal length information Zp. Read. This drive control unit 12a
Upon receiving the start signal (STR) from the camera, the variable power control unit 16 drives the variable power lens group 2 in the telephoto direction.

Next, the focus correction calculation unit 11a receiving the outputs Fpx and Cfp of the maximum feeding amount calculation unit 9 and the proportional constant calculation unit 10 outputs a correction amount (Dfp). Focus correction amount calculation unit 11b receiving this
Is a focus correction control amount obtained by adding a focus shift correction amount described later.
Dfp 'is output to the drive control unit 12a. In response, the drive control unit 12a outputs a correction drive signal (Dfcd). Above (Dfc
In response to d), the focus control unit 12 controls the focusing lens group 3
It corrects a focus shift caused by a scaling operation that drives by an amount corresponding to the correction drive signal (Dfcd). Note that the concept is the same when the operation switch 13 is closed to the down contact 13b side, and the description of the operation is omitted.

Next, the AF operation will be described. The shooting distance detector 17 measures the subject distance and outputs distance measurement data (AF) corresponding to the measured distance. The focus correction calculation unit 11a receives this, calculates the drive amount of the focusing lens group 3 up to the in-focus position, and further receives outputs from the maximum extension amount calculation unit 9 and the proportional constant calculation unit 10, Calculate the limited drive amount. The drive control unit 12a determines whether or not the focusing lens group 3 is located on the close side or in the ∽ side limit zone based on the presence or absence of the limit signal (Lm). If it is located within the ∽ side restriction zone, the focus correction amount calculation unit 11
Check the direction component of the focus correction control Dfp 'from b,
If it is the direction, a prohibition signal (H) is output to prohibit the focusing operation. When the directional component is on the near side, the focusing correction control amount Dfp 'is compared with the limit driving amount, and if Dmax> Dfp, a focusing operation corresponding to the focusing correction control amount Dfp' is executed. , If Dmax ≦ Dfp ′, the drive limit is forced to Dfp
Output as

FIG. 3 is a flowchart for explaining the operation of the main part of this embodiment, and FIG. 4 shows the relationship between the focus correction control time and the focus correction amount using the motor drive voltage as a parameter. It is a characteristic diagram.

Here, the operation of the focus correction amount calculating means of the embodiment shown in FIG. 1 will be described in detail with reference to FIG. 2, FIG. 3, and FIG.

For the sake of simplicity, the description will be made on the assumption that, at the initial stage, the variable power lens group 2 is at the wide end and the focusing lens group is at a position where the object distance is 2.0 m. Proceed.

In the "focusing lens group position detecting (Sx)" in the flowchart shown in FIG. 3, the detecting the focus position information Sx ₁ through FPM7, then "zoom lens group position detecting (Zp)",
Detecting the focal length information Zp ₁ by ZPM8. The "maximum movement amount calculation (Fpx)", based on the detected focal length information Zp ₁ as described above, the maximum movement amount calculating section 9, the maximum movement amount Fpx ₁ by the following equation (2) Ask.

Fpx ₁ = [C ₂ / (C ₁ + Zp ₁ )] + C ₃ (2) Proportional constant calculator based on the data of the maximum feed amount Fpx ₁
10 calculates the proportionality constant Cfp by the following equation (3), and sends the information to the focus correction calculation unit 11a.

Cfp = (Sx ₁ / fpx ₁ ) · C ₄ (3) In the formulas (2) and (3), C ₁ , C ₂ , C ₃ , and C ₄ are set constants determined at the time of design. It is.

Here, the changeover switch 14 is turned on, and the operation switch
Assuming that the operation is performed so that 13 is connected to the up contact 13a side, as described above, the activation signal STR in the magnification increasing direction is output from the drive control unit 12a, and the variable power control unit 16 drives the variable power motor Mz. The focusing lens group 3 moves to the telephoto side.

Assuming that the focus correction operation is performed at the time of the focal length f, for example Zp _2, ZPM8 the new focal length (50 mm)
Detects information Zp _2, on this basis, the maximum movement amount calculating section 9, the maximum feeding amount Fpx ₂ = _{[C 2 / (C 1 + Zp} 2) ] + C ₃ in Zp ₂ by the equation (1) .

Next, in the “focus correction calculation (Dfp)” of the flowchart, the focus correction calculation unit 11a performs the above-described maximum feed amount Fpx ₂
And the proportional constant Cfp as input information, and calculates a correction amount Dfp by the following equation (4).

Dfp = (Cfp / C ₄ ) · Fpx ₂ −Sx ₁ (4) In the next “focus correction permitted?”, Focus correction control is executed based on information such as whether or not the camera is in the control band. Is determined. If this “focusing correction allowed?” Branches to YES, the “magnification moving amount calculation (Dz
In p), a time for performing focus correction control on the correction amount Dfp obtained by the equation (4) is predicted and calculated, and at this time, the zooming movement amount Dzp at which the zooming lens unit 2 moves is determined by the motor drive voltage or motor rotation. Calculate in consideration of speed, etc. The new focal length information Zp accompanying the movement of the zooming movement amount Dzp in “Maximum extension amount calculation (Fpx ′) with the zooming lens group position as Zp + Dzp”
_{3 Based on} (Zp ₂ + Dzp), the maximum feeding amount Fpx ′ at the focal length is calculated by the above equation (2).

In the “focus correction calculation”, the focus correction amount calculation unit 11b calculates the focus correction control amount Dfp at the focal length position (Zp ₂ + Dzp).
₃ is calculated by the following equation (5).

Dfp ₃ = (Cfp / C ₄ ) · Fpx′−Sx ₁ (5) The control time of the focus correction control amount Dfp ₃ obtained here is based on the characteristic diagram and the focus correction amount shown in FIG. since due largely changed, which was considered corresponding by varying the constants C ₅ in the following equation (5).

Dfp ′ = Dfp ₃ × C ₅ (6) In other words, the focus correction control amount Dfp ′ is obtained by the focus correction amount calculation means including the focus correction amount calculation unit 11b and the focus correction calculation unit 11a.
The calculated, by the amount corresponding thereto, the drive control section 12a, by performing the focus correction control by the focus control section 12 and the focus motor M _F, a point on the focusing curve 22 shown in FIG. 2 DF
The focusing lens group 3 can be accurately positioned at C.

Therefore, with the configuration as in the above embodiment, it is possible to perform ideal focusing control without a focus shift such as the curve a in the focusing correction control diagram shown in FIG. In this case, useless operation is eliminated, and a quick zooming operation can be performed.

It should be noted that the present invention is not limited to the above-described embodiment,
Various modifications can be made without departing from the scope of the invention.

For example, when calculating the zooming movement amount of the zooming lens group 2 during the focus correction control operation, the moving speed of the zooming lens group 2 itself or the rotation speed of the zooming motor Mz is detected, and the detection result is obtained. Is preferably added to the calculation, but the moving speed of the variable power lens group 2 may be regarded as constant (constant).

Further, it has been described that the output (Dfp ′) of the focus correction amount calculation unit 11b is temporarily received by the drive control unit 12a and is output as the correction drive amount (Dfcd). Is also good.

〔The invention's effect〕

As described in detail above, according to the present invention, the focus correction tracking delay of the focusing lens group accompanying the variable power movement of the variable power lens group during the focus correction control operation as in the related art is caused. Focus shift is prevented, and the follow-up performance of the focus lens group during focus correction is significantly improved, so that useless operation can be avoided, enabling quick lens drive and saving drive energy. It is possible to provide a varifocal lens control device capable of improving operability as a whole.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of one embodiment of a varifocal lens control device according to the present invention. FIG. 2 is a block diagram showing the total system focal length f to be set in the embodiment shown in FIG. FIG. 3 is a diagram illustrating the relationship between the focus lens group extension amount Sx corresponding to the subject distance D for each subject distance and explaining the focus correction control operation. FIG. 3 illustrates the operation of the present embodiment. FIG. 4 is a characteristic diagram showing a relationship between a focus correction amount and a focus correction control time using a motor drive voltage as a parameter, and FIG. 5 is a conventional focus correction control state of a varifocal lens. FIG. 1 ... optical axis, 2 ... variable lens group, 2a to 2e ... first lens group to 5th lens group, 3 ... focusing lens group, 4 ... variable magnification drive unit, 5 ... focus drive Section 6 Focus counter 7 Focusing lens group position detector (FPM) 8 Magnifying lens group position detector (ZPM) 9 Maximum feeding amount calculation section 10 Proportional constant Calculation unit, 11a: Focus correction calculation unit, 11b: Focus correction amount calculation unit 12, Focus control unit, 12a Drive control unit, 13 Operation switch, 14 Changeover switch, 15 Lens position determination unit, 16: Variable magnification control unit, 16a: Back electromotive voltage detection unit, 17: Shooting distance detection unit, 18: Display unit, 19 to 24: Focusing curve.

Claims (1)

(57) [Claims] In a variable power optical system including a variable power lens group and a focusing lens group disposed on the same optical axis, the relationship between the object distance and the extension amount of the focusing lens group in the optical axis direction is determined. In a varifocal lens that differs at the magnification position within the zoom range,
Focus driving means for driving the focusing lens group, variable power driving means for driving the variable lens group, and focusing lens group position detecting means for detecting the position of the focusing lens group on the optical axis And a variable power lens group position detecting means for detecting a position on the optical axis corresponding to the focal length of the variable power lens group,
Receiving the focusing lens group position information and the zooming lens group position information output from the focusing lens group position detecting means and the zooming lens group position detecting means, respectively, and accompanying the zooming movement of the zooming lens group. The resulting imaging position shift is calculated as a correction amount, and a focus correction time for performing the focus correction on the correction amount by the focus lens group is calculated, and the focus change time of the variable power lens group during the focus correction time is calculated. A focus correction amount calculating means for calculating a focus shift correction amount in consideration of a zooming movement amount, and calculating a focus correction control amount obtained by adding the correction amount and the focus shift correction amount; and the focus correction Focus correction control means for receiving the information on the control amount and controlling the focus drive means to drive the focus lens group to a focus position at a focal length at the time when the focus correction time has elapsed. And the focal length of the entire system Varifocal lens control apparatus of the imaging position deviation caused by the new characterized by being configured to automatically correct control while performing the zooming movement of the group the variable power lens.