JPS63293513A - Control device for variable focal lens - Google Patents

Abstract

PURPOSE:To simplify a variable power driving means by receiving the output of a focusing lens group position detector and a focal distance detector to control the variable power driving means, calculating the correction value of an image forming position deviation and driving focusing lens groups to focusing positions. CONSTITUTION:A maximum delivering distance arithmetic part 9 receives an output Zp from the focal distance detector 8 and outputs a lens delivering distance Fpx and focus position information at an infinite position. A proportional constant arithmetic part 10 receives an output Sx from the focusing lens group position detector 7 and the delivering distance Fpx and calculates a proportional constant Cfp. A variable power control part 16 rotates a variable power motor MZ. Since a focus motor MF is not driven, focusing lens groups 2a, 2b are held at fixed positions. Every movement of the variable power constitutional group by a prescribed distance, the lens groups 2a, 2b are driven by a focus control part 12. Since the control device is constituted so that the focus positions are changed by the outputs Zp, Sx in said constitution, the moving distances of the lens groups, 2a, 2b on the wide side are not unnecessarily increased.

Description

Detailed Description of the Invention (a) Technical Field The present invention relates to a varifocal lens control device, and more particularly to a varifocal lens control device comprising a variable power lens group and a focusing lens group arranged on the same optical axis. After setting the focusing lens group of the optical system to a focusing position between a close position and an infinity position on the optical axis corresponding to a subject distance ranging from a close distance to an infinite distance, the variable magnification lens group By updating the entire focal length of the variable magnification optical system from an arbitrary first focal length to a second focal length between the shortest focal length and the longest focal length, the image forming position shifts for the same subject. This invention relates to a control device for a varifocal lens that produces varifocal lenses.

(b) Conventional zoom lenses do not shift the imaging position (so-called focus movement or focus deviation) even when zooming, so there is no need to bother with adjusting the focus for each zooming operation, and the operability is good. Open aperture F compared to a single focal length lens
Because the numbers are dark, a certain degree of skill is required to adjust the focus (focusing operation) using, for example, an eye reflex finder. In recent years, with the advancement of cameras with AF, this problem has been solved and the inherent mobility of zoom lenses can be demonstrated, allowing the operator (user) to focus only on determining the composition according to the intention of the image. This has greatly improved operability.

In general, focusing (focusing operation) of a zoom lens is
This is accomplished by moving a focusing lens group disposed as part of the variable magnification optical system. In a zoom lens, the amount of movement of this focusing lens group is almost the same for the same subject distance in the entire zoom range (hereinafter referred to as
Therefore, the object distance scale is attached to the moving member (distance ring) of the focusing lens group, while the index is attached to the fixed ring disposed adjacent to it. This has the advantage that it is only necessary to attach the lens, and there is no need to change the subject distance scale according to zooming. However, although it varies depending on the lens configuration of the variable power optical system, inner focusing type and rear focusing type zoom lenses have
When performing optical design under the condition that the above-mentioned equal displacement is achieved, there is a problem that the lens configuration becomes complicated.
Furthermore, there is a problem in that the amount of movement (extension) of the focusing lens group on the wide-angle side becomes unnecessarily large.

This also causes the problem that the outer diameter of the lens becomes large, which increases the weight of the lens and lens barrel.

As mentioned above, the operability of zoom lenses has been improved by combining them with the AF function, but they cannot escape from the above-mentioned condition of equal movement that zoom lenses have, so it is necessary to make them more compact and lower costs. The problem remained that it was difficult to realize.

Therefore, the present applicant has proposed an invention (hereinafter referred to as the "prior invention") relating to a varifocal lens control device that can solve the above-mentioned problems.
) was previously proposed in Japanese Patent Application No. 1983-013345.

That is, the above-mentioned prior invention is capable of adjusting the focusing lens group of a variable magnification optical system consisting of a variable magnification lens group and a focusing lens group disposed on the same optical axis to a subject distance ranging from a close distance to an infinite distance. After setting the focusing position between the closest position and the infinity position on the corresponding optical axis, the variable magnification lens group sets the overall focal length of the variable magnification optical system to the shortest focal length and the longest focal length. In a varifocal lens that causes an image formation position shift for the same subject when updating from an arbitrary first focal length to a second focal length between , a focusing lens group position detection means for detecting the position of the focusing lens group on the optical axis; and a focusing lens group position detecting means for detecting the position of the focusing lens group on the optical axis; and a focusing lens group position detecting means for detecting the position of the focusing lens group on the optical axis; Maximum extension amount calculation means for calculating the extension amount to the closest position; Proportionality constant calculation means for receiving the outputs of the maximum extension amount calculation means and the focusing lens group position detection means, respectively, and calculating the ratio of these outputs. , receives the outputs of the proportional constant calculating means, the maximum extension amount calculating means, and the focusing lens group position detecting means, respectively, and calculates the amount of deviation of the imaging position from the in-focus position that occurs as the overall system focal length is updated. A focusing correction calculation means for calculating a correction value, a focusing driving means for driving the focusing lens group, a movement amount monitoring means for generating a signal corresponding to the movement amount of the focusing lens group, and this movement amount. Focusing control means for controlling the focusing lens group to drive the focusing lens group to the focusing position in response to the outputs of the monitoring means and the focusing correction calculating means, respectively; and a variable power driving means for driving the variable power lens group. and a magnification control means for controlling the magnification variable driving means in response to a start signal from a separately provided start means, and automatically corrects the image formation position shift due to updating of the overall focal length of the magnification variable optical system. It is configured to correct the

According to the prior invention configured in this way, the lens optical system itself has a very simple configuration, is small, lightweight, and inexpensive, and the entire lens control device is also small, lightweight, inexpensive, and variable. Even if you move the magnification lens group from the first focal length to the second focal length and update the focal length of the entire system, the image formation position shift peculiar to varifocal lenses is instantly corrected and the in-focus state is maintained. Therefore, it is possible to obtain a lens that is substantially equivalent in usability to a zoom lens.

However, as will be explained in detail later, with the varifocal lens, even though the overall focal length changes from the shortest focal length to the longest focal length, the in-focus position at infinity (co position) does not change; The focusing position is configured to change away from the infinity position, and the focusing operation is performed by moving each of a plurality of focusing lens groups disposed in a part of the variable magnification optical system. It is supposed to be done in Each focusing lens group normally has a cam frame for driving the focusing lens group (
The lens is moved in the optical axis direction by a cam groove formed in the focus cell (hereinafter referred to as "focus cell"), and a predetermined lens is moved by a plurality of cam grooves formed in the variable power lens group drive frame (hereinafter referred to as "variable power cell"). Intervals are now set. Therefore, since each focusing lens group is connected to the cam frame for driving the variable power lens group (hereinafter referred to as the "variable power cell") through different cam grooves, it is inevitable that the variable power lens group The mechanical parts that drive both of the focusing lens groups have become complicated, which has been an obstacle to simplifying the configuration, reducing costs, and making it more compact.

(c) Purpose The present invention was made in view of the above-mentioned circumstances, and its purpose is to temporarily change the focusing lens group while using a varifocal lens, which is an inexpensive, small, and simple optical system. After focusing, change the focal length of the entire system from an arbitrary first focal length to a second focal length between the shortest focal length and the longest focal length.
It automatically corrects the image formation position shift peculiar to varifocal lenses when updating to a focal length of An object of the present invention is to provide a varifocal lens control device that can realize a reduction in .

(d) Structure In order to achieve the above-mentioned object, the present invention provides a variable power optical system consisting of a variable power lens group and a focusing lens group arranged on the same optical axis. After performing a focusing operation to set a focus position on the optical axis from the closest position to the infinity position corresponding to the subject distance reaching infinity, the variable magnification optical system is set by the variable magnification lens group. Varifocal, which causes a shift in the imaging position for the same subject due to the magnification change operation that updates the entire system focal length from the first focal length to the second focal length, which is arbitrary between the shortest focal length and the longest focal length. In the lens, the variable magnification lens group includes a plurality of lens groups that move in the optical axis direction as the magnification changes, and the variable magnification lens group further moves in the optical axis direction as the focusing operation occurs. The above-mentioned focusing lens group consisting of at least two or more moving lenses, and one of this focusing lens group
variable power lens group position detection means for outputting position information corresponding to the position on the optical axis of the variable power component group consisting of the remaining variable power lens groups except for the two lens groups; and an optical axis of the focusing lens group. a focusing lens group position detection means for outputting position information corresponding to the above position; a variable power driving means for driving the variable power component group; a focusing drive means for driving the focusing lens group; Controls starting and stopping of the variable power drive means upon receiving the outputs of the lens group position detecting means and the focusing lens group position detecting means, respectively, and calculates a correction amount to correct the image formation position shift caused by the variable magnification operation. The present invention is characterized by comprising a variable magnification focus correction control means for controlling the focus drive means to calculate and drive the focus lens group to the focus position.

Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the overall configuration of the present invention. In FIG. 1, 1 is the optical axis of the variable power optical system, and 2 is a varifocal lens that is movably disposed on the optical axis 1 and constitutes the variable power optical system. Variable magnification lens group, 2a.

2b, 2c, 2d, and 2e are a first group lens, a second group lens, a third group lens, a fourth group lens, and a fifth group lens, each consisting of a single lens or a plurality of lenses.

The first group lens 2a and the second group lens 2b constitute a focusing lens group as a focusing lens group. This first group.

Including the second group lenses 2a and 2b, and the third group lenses 20 to 20.
The variable magnification lens group 2 is composed of the fifth lens group 2e. Note that the variable power lens group excluding the second lens group 2b constitutes a variable power component group.

Further, the overall focal length of the variable magnification optical system including the variable magnification lens group 2 is f. 3 is the film plane, and 4 is the telephoto side focal length where the entire system focal length f is the longest focal length (hereinafter simply "
The zoom lens is a lens that drives the variable magnification component group to set an arbitrary focal length between the shortest focal length (hereinafter simply referred to as the "wide-angle side") and the shortest focal length (hereinafter simply referred to as the "wide-angle side"). A variable magnification drive section 5, which is composed of a variable magnification motor Mz as a magnification drive means and a mechanism section to be described later, is a variable magnification drive section 5 which is a variable magnification drive section 5 which is a variable magnification motor Mz as a multiplication drive means, and a variable magnification drive section 5 which is a variable magnification drive section 5 that is a variable magnification drive section 5 which is a variable magnification drive section 5 that is a variable magnification drive section 5 that is a variable magnification drive section 5 which is a variable magnification motor Mz as a multiplication drive means and a mechanism section to be described later. The first group lens 2 is placed at the focusing position between
a and the second group lens 2b (in detail, the first
A focus motor MF (which moves the group lens 2a and the second group lens 2b in the optical axis direction while keeping the interval constant) and a focus drive section 6 and 7 each include a mechanism section to be described later. Together with the first group lens 2a and the second group lens 2b, the focus drive section 5 drives the focus drive section 5, and among these, 6 receives pulses proportional to the rotation speed from the photointerrupter 6b by rotationally driving the slit disk 6a. occurs and the first group lens 2
a and a focus counter that detects the amount of movement of the second group lens 2b on the optical axis 1; and 7, a voltage proportional to the position of the first group lens 2a and the second group lens 2b on the optical axis;
A focusing lens group position detector (hereinafter referred to as rF
(abbreviated as PMJ), 8 is driven by the variable magnification drive unit 4 together with the variable magnification component group to apply a voltage proportional to the focal length f of the entire system.
A variable power lens group position detector (hereinafter referred to as rZPMJ) serves as a variable power lens group position detection means that outputs focal length information Zp.
), 9 receives the above focal length information Zp and A/
A maximum extension amount calculation unit that calculates the amount of movement (i.e. extension amount) Fpx of the first group lens 2a and the second group lens 2b from the ψ position to the closest position at this Zp after D conversion; 10 is this maximum extension amount. Outputs FρX and FP of the quantity calculation unit 9
After receiving the output Sx as the focus position information of the M7, A/D converting the output Sx, and calculating the ratio thereof,
11 is a proportional constant calculation unit that outputs a proportionality constant Cfp; 11 is a focus correction calculation unit that receives the above three outputs Fpx, Cfp, and Sx and calculates a correction amount Dfp for focusing; 12
is a focus control section that controls the focus drive section 5 in response to the output Dfc of the focus counter 6 and the output Dfp corresponding to the correction amount of the focus correction calculation section 11.

Reference numerals 13 to 15 constitute starting means, and 13 and 14 are variable power switches each consisting of an externally operable push button switch for starting variable power operation.

13 is a magnification up switch (hereinafter simply referred to as "up switch"), 14 is a magnification down switch (hereinafter simply referred to as "down switch"), and 15 is a switch 13.
．． A drive direction determining section receives the output of 14, determines the rotation direction of the variable magnification motor Mz, and outputs a start signal (STR); 16 receives the start signal STR and the output FρX and controls the variable magnification drive section 4; This is a variable magnification control section.

Here, the maximum extension amount calculation section 9, the proportional constant calculation section 10, the focus correction calculation section 11, the focus control section 12, and the zoom control section 16 constitute a zoom/focus correction control means. Note that +v indicates a power supply, and the input/output relationships of each part indicate only main signals.

Now, the contents of the calculations executed by each of the above-mentioned calculation units and the calculation formulas related thereto are shown below.

Conventional zoom lenses are defined as ones that do not move the focus due to zooming operations (updating the overall focal length f), but the basic idea of the present invention is to first allow the focus movement (the final (In general, this focus movement is corrected to bring the camera into focus.)

Note that the focusing method is not scattered and is assumed to be a front focusing method. The maximum feeding amount calculation unit 9 outputs an output corresponding to the feeding amount from the infinite position to the closest position as Fp.
x, the output of ZPM8 is ZP, and the constant specific to the lens of the variable magnification optical system is C, respectively.

When C,,C3, ” (1) Fp””　Zp+C8+C・ Execute the calculation using the calculation formula.

Furthermore, the same maximum feeding amount calculating section 9 is operated as shown in FIG.
Assume that the focus position information Sx corresponding to the cam diagram at the ω position of the group lens 2a is 5x(oo).

Calculate using the following formula. However, here 2ρ is the above ZP
The outputs of M8, A, , A□, and A2 are constants specific to the lens of the variable magnification optical system, as described above.

The proportional constant calculation unit 1o calculates the output of the FPM 7 immediately before the start of the operation of the variable magnification drive unit 4 as 5(i),
Cfp is the output of
The output of the maximum feed amount calculation unit 9 based on the output of PM8 is expressed as Fp(
When i), the following calculation formula is executed.

Further, the focus correction calculation means 11 calculates the output of the focus correction calculation unit 11 at predetermined time intervals after the start of the operation of the variable magnification drive unit 4, or at the time when the change in the output from the ZPM 8 reaches a predetermined amount. 5(e), the output of the proportional constant calculation unit 10 is Cfp, the output ZP of ZPM8 at the time of correction and the above 5x(
When the values of oo) are respectively Zpl and Sl, 5(e)=Cfp-Fp (e)+S,
(4) is used to calculate the expected focus position S (e).

However, Fp(e) is a value obtained by substituting ZP=ZPt into equation (1). The basic idea of the present invention is the following equation (5), from which the above equations (1) to (4) are derived.

D=(CO-7p+C1)・Sx+C2(5) Here,
In D, the subject distances C0, C1, and C2 are setting constants determined at the time of design.

In other words, in equation (5), if a means for controlling ZP and Sx is realized so that the subject distance does not change, it becomes possible to eliminate (correct) the shift in focus caused by the magnification change operation. However, the amount of movement of the focusing lens group is not the same amount as described above. In other words, the theory of the present invention can be said to be a theory that actively removes the condition of equal movement.

FIG. 2 is a cam diagram showing the movement of the variable power component group of the apparatus of the present invention shown in FIG. 1, and shows the case where the focal length f of the entire system is updated from the wide side to the telephoto side, for example. Sx is the above-mentioned focus position information Sx, and in this drawing, the amount of extension (amount of movement) corresponding to the subject distance of the focusing lens group (first group lens 2a and second group lens 2b)
It shows. Zp is also the above-mentioned focal length information Zp, and in this figure, the amount of movement due to the variable power operation of the variable power lens group 2 is shown with the fourth group lens 2d as a representative thereof. Also,
In this drawing, 1 is the optical axis 1' on the wide side.
is the optical axis on the telephoto side.

FIG. 3 is a vertical cross-sectional side view showing the structure of the mechanical parts of the variable magnification drive section 4 and focus drive section 5, which were not specifically shown in FIG. 1, and FIG. 5(b) is a partial sectional view taken along the line AA' in FIG. 5(a).

In FIG. 3, 17 and 18 to 19 are a first group cell and a third group cell to a fifth group that fixedly support the first group lens 2a and the third group lens 20 to the fifth group lens 2e, respectively.
It is a group cell. 21 and 22 to 24 are first pins and third to fifth pins protruding from the first group cell 17 and third group cell 18 to fifth group cell 20, respectively, in a direction substantially perpendicular to the optical axis 1. It's a bottle. 25 is a fixed cell having a cylindrical cross section which is an immovable member, and 26 is a fixed cell 2 that is a fixed member.
The first half of the fixed cell 25, 27, is smaller in diameter than the first half 26, and the second half of the fixed cell 25, 28 and 29 to 31, are
The first bin 21 and the third pin 22 to the fifth bin 2, respectively.
4 is a linear cam groove of the fixed cell 25 that is bored at a position above the fixed cell 25 and has a width that allows the insertion of the linear cam groove. Reference numeral 32 denotes a variable power cell rotatably fitted into the outer periphery of the rear half 27 of the fixed cell 25 in a state where movement in the optical axis direction is prevented. The gear portion 33b formed on the outer periphery of the flange portion is also a rotation transmission pin protruding from the front end of the variable power cell 32 substantially perpendicular to the optical axis 1.
34 is a variable power transmission cell fitted into the inner periphery of the front half 26 of the fixed cell 25 so as to be rotatable and also movable in the optical axis direction;
34a has a length corresponding to at least the amount of movement of the variable power transmission cell 34 in the optical axis direction, and the rotation transmission pin 33b
A notch 35 is formed along the optical axis 1 from the rear end of the variable power transmission cell 34 and has a width into which the variable power transmission cell 34 can be inserted. The fixing portion 36 is a cam groove drilled in the variable power transmission cell 34 with a width into which the first pin 21 can be fitted, and 37 to 39 are cam grooves into which the third pin 22 to the fifth pin 24 can be fitted, respectively. A cam groove with a width is formed in each of the variable power cells 32, 40 is a focus transmission cell fitted into the outer periphery of the front part 26 of the fixed cell 25 so as to be movable only in the optical axis direction, and 40a and 40b are cam grooves. Focus pins 41 and 42 protrude from the outer periphery and inner periphery of the focus transmission cell 40 in a direction perpendicular to the optical axis 1, respectively. and a linear cam groove and a cam groove respectively formed in the variable power transmission cell 34; 43 is a focus cell that is rotatably fitted into the outer periphery of the focus transmission cell 40 and whose movement in the optical axis direction is regulated; 43a is a focus cell; A gear portion 43b formed on the outer periphery of a flange portion provided at the rear end of the focus cell 43 is the focus pin 40a.
44 is the focus motor MF explained in FIG. , 45 is a variable power motor Mz, and 45a is a driving gear that meshes with the gear portion 33a of the variable power cell 32 and is driven by the variable power motor Mz. In the following FIGS. 4 to 8, the same parts as in FIG. 3 are given the same reference numerals, and redundant explanation will be omitted.

FIG. 4 shows the linear cam groove 29 in the rear half 27 of the fixed cell 25.
31 and cam grooves 37 to 39 of the variable power cell 32. The linear cam grooves 29 to 31 are each formed into a long hole along the optical axis direction.

The cam grooves 37 to 39 of the variable power cell 32 are formed into elongated holes shaped along a cam diagram determined when the variable power lens group 2 is designed.

5(a) and 5(b) are enlarged views of the connecting portion between the variable power cell 32 and the variable power transmission cell 34.
Figure (a) is a plan view of the above-mentioned connecting part in Figure 3, Figure 5 (b)
is a sectional view taken along the line AA' in FIG. 5(a).

In FIGS. 5(a) and 5(b), the notch 34a
is a straight elongated notch along the optical axis 1, and the rotation transmission pin 33b is fitted into this notch 34a. Therefore, the variable power transmission cell 34 is configured such that its position is not restricted by the variable power cell 32 with respect to movement in the optical axis direction, and only the rotational movement of the variable power cell 32 is transmitted.

FIG. 6 is an enlarged plan view from the third focus transmission cell 4o side showing the cam shapes and relationship between the front half 26 of the fixed cell 25 and the variable power transmission cell 34. The cam groove 36 of the variable power transmission cell 34 is formed in a shape along a cam diagram determined when the variable power lens group 2 is designed. Therefore, the first group cell 17 is configured to move along the optical axis along with the rotational movement of the variable power transmission cell 34 and perform a variable power operation independently of the single focusing operation.

FIG. 7 is an enlarged plan view showing the shape of the cam groove 43b of the focus cell 43 and the directional relationship of the optical axis 1. As can be seen from the figure, it is formed in a shape that forms a predetermined inclination with respect to the optical axis 1. Therefore, the rotational movement of the focus cell 43 is converted into a linear movement of the focus pin 40a in the optical axis direction, that is, a linear movement of the focus transmission cell 40 in the optical axis direction.

FIG. 8 is an enlarged plan view seen from the focus cell 43 side showing the relationship between the focus cell 40, the front half 26 of the fixed cell 25, and the variable power transmission cell 34, and the shapes of their respective cam grooves. The linear cam groove 41 of the front half 26 is formed as a linear long hole extending along the optical axis. The cam groove 42 of the variable power transmission cell 34 is formed to be orthogonal to the linear cam groove 41. In other words, the rotational movement of the variable power transmission cell 34 accompanying the female magnification operation is not restricted by the focus pin 40b of the focus transmission cell 40. In addition, in FIG. 3, the front half 26 of the fixed cell 25
Although the linear cam groove 28 and the linear cam groove 41 are shown as having the same cross section for convenience of drawing, the linear cam groove 2
8 and the linear cam groove 41 are located on different cross sections.

Next, the operation of this embodiment configured as described above will be explained.

Before describing the overall control operation, the operation of the mechanism shown in FIG. 3 will be explained.

First, the driving gear 45a is rotated by the variable power motor 45, and rotational motion is transmitted to the gear portion 33a that meshes with the driving gear 45a. The lens group 2b begins to rotate integrally. First group cell 17, and third group cell 18~
The fifth group cell 20, as shown in FIGS. 6 and 4,
Each of the first pin 21 and the third pin 22 to the fifth pin 24 has a linear cam groove 28° 29 along the optical axis direction.
．． 30 and 31 regulate the position in the direction of rotation. Therefore, the variable power transmission cell 34 and the variable power cell 32
Due to the rotation of
39 on the optical axis. That is, each of the first lens group 2a to fifth lens group 2e, excluding the second lens group 2b, moves according to the cam diagram shown by the solid line in FIG. 2, respectively. Although the focal length f can be updated by this magnification change operation, a focus shift also occurs, which must be corrected. Therefore, next we will discuss the focusing operation. Note that the second group lens 2b is not moved by the above-mentioned zooming operation.

The driving gear 44a is driven by the focus motor 44, and its rotational force is transmitted to the gear portion 43a of the focus cell 43 that meshes with the driving gear 44a, causing the focus cell 43 to rotate, as shown in FIG. Since the position of the focus pin 40b is restricted in the rotational direction by the linear cam groove 41 formed in the front half 41 of the fixed cell 25, the focus transmission cell 4o cannot also move in the rotational direction, and therefore, as shown in FIG. The focus pin 40a fitted into the cam groove 43b of the focus cell 43 moves linearly on the optical axis by an amount according to the horizontal force component in the figure with respect to the rotation angle of the cam groove 43b.

In other words, the rotational motion of the focus cell 43 is converted into a linear motion of the focus transmission cell 40 in the optical axis direction via the focus pin 40a, and this linear motion is further transmitted to the variable power transmission cell 34 via the focus pin 40b. 1
The entire variable power transmission cell 34 moves on the optical axis while maintaining the lens interval between the group lens 2a and the second group lens 2b set by the above-mentioned variable power operation (however, the second group lens 2b does not move). The lens then reaches the in-focus position. As is already clear from this description, the variable power transmission cell 34 is involved in both the variable power operation and the focusing operation. still,
The change in the output of the ZPM 8 due to the above zooming operation is Zp shown in FIG. 2, and the change in the output of the FPM 7 due to the above focusing operation is Sx shown in FIG. 2 as well.

Next, the overall control operation of this embodiment will be described using FIG.

First, to explain the magnification increasing operation from the wide side to the telephoto side, when the up switch 13 in FIG. . The maximum feed amount calculation section 9 receives the output (Zp) of the ZPM8 and performs A/D conversion, and the proportionality constant calculation section 10 receives the output (Sx) of the FPM 7 and converts it into A/D.
/D conversion, for example Zp respectively. and S (i). The maximum feed amount calculation unit 9 calculates FρX at this time using equation (1), and further calculates 5 using equation (2).
x(oo) is calculated, and the proportionality constant calculation section 10 also receives the Fpx and calculates the proportionality constant Cfp using equation (3).

Next, the magnification control unit 16 rotates the magnification motor Mz in the direction of increasing the magnification. Then, the variable magnification lens group 2 moves according to the variable magnification operation shown in FIG.
) also changes as shown in FIG. However, FPM7
Since the focus motor MF is not operating, the distance between the first group lens 2a and the second group lens 2b changes according to the cam shape of the variable power transmission cell 34 shown in FIG. 6, as described above. The lens group is held at a fixed position and does not change when the magnification is changed. The focusing lens groups 2a and 2b are driven by the focus control section 12 every time the variable power component group moves by a predetermined amount (for example, 8 steps). In other words, the zoom motor Mz continues to rotate even during the focus correction operation by the focus motor MF, and the focus control unit 12 further controls the output Dfc of the focus counter 6 and the planned focus position S (e ) and Dfc=S
When (e) is reached, the focusing motor MF
is stopped to complete one cycle of the magnification increase operation.

Thereafter, similar operations are repeated until the up switch 13 is turned off. Therefore, from a macroscopic perspective, there is no out-of-focus caused by the magnification change operation, and although it is a pari-focus lens, it apparently functions like a zoom lens.

As described above, this embodiment removes the above-mentioned condition of equal movement in conventional zoom lenses and is configured so that the change in focus position at each subject distance is expressed by equation (5). This has the advantage that the amount of movement of the focusing lens groups 2a and 2b does not become unnecessarily large. Therefore, there is an advantage that the outer diameter of the lens can be made as small as possible. Moreover, in terms of appearance (in use), it has the advantage that, like conventional zoom lenses, no focus movement (blurring) occurs even if the magnification is changed after focusing once.

Furthermore, since the second group lens 2b is fixed to the variable power transmission cell 34, the cell for the second group lens can be omitted, and there is no need to form a cam groove, which is difficult to process, in the variable power transmission cell 34. Therefore, it is possible to simplify the configuration and reduce costs. In addition, since there is no need to drive the second lens group 2b to change its magnification, the frictional force is reduced accordingly, and therefore, it is also possible to reduce drive loss.

In addition, since mechanical focusing correction using a conventional cam is performed electrically, the outer diameter of the lens can be made as small as possible, as mentioned above, and the lens barrel configuration can be simplified, so that the motor that drives the focusing lens group can be It has the advantage that a small capacity is sufficient and the entire device can be made smaller, lighter, and lower in cost. Especially when using the camera and this device in conjunction,
Since the AF circuit of the camera can be shared, there is an advantage that costs can be further reduced.

It should be noted that the present invention is not limited to the above-described embodiments, and can be modified in various ways without departing from the spirit thereof.

For example, the cells fixed to the variable power transmission cell 34 may be the first group cells 17.

Further, the variable power transmission cell 34 is involved in the zooming operation and the opening operation of the focusing operation, but as shown in FIG. 3, the focus counter 6 and the FPM 7 are connected to the driving gear 44a. The present invention is not limited to this example, and the configuration may be such that the amount of movement of the focus cell 43 and the focus transmission cell 40 in the optical axis direction is detected.

Similarly, the ZPM 8 is not limited to the example in which the configuration is connected to the driving gear 45a, and the rotation angle of the variable power cell 32 or the variable power transmission cell 34, or the third group cell 19 to the fifth group cell 2
1 may be configured to detect the amount of movement in the optical axis direction.

Further, the focus motor 44 and the variable magnification motor 45 are
They may be driven via a speed reduction mechanism or the like without being directly connected to the driving gears 44a and 45a, respectively.

Further, the planned focus position S (e) may be compared with the output of the FPM 7 without comparing it with the output Dfc of the focus counter 6, if there is no problem with accuracy.

In other words, the focus motor MF may be configured to stop when 5x=S(e).

In addition, the arithmetic expression Fpx in the form of Taylor expansion of equation (1)
=a0+a-Zp+a2Zρ2... It may be done.

Here, a,, a□, a2. . . . are setting constants determined at the time of design.

Furthermore, in general, at the stop positions on the telephoto side and the wide side, due to the problem of the pressure angle between the zoom cam and the stop member, that is, the stop strength, there are cases where an arithmetic expression such as equation (1) cannot be approximated on the telephoto side and the wide side. In that case,
This can be done by dividing the Zp zone into three zones and creating an approximate expression for each zone.

Further, equation (1) and the like are limited to calculations, and the data can also be stored in the CPU and ROM.

(e) Effects As explained in detail above, according to the present invention, the lens optical system itself has a very simple configuration and uses a small, lightweight, and inexpensive varifocal lens. By configuring one of the lenses not to be driven by the variable power driving means, it is possible to realize an i-element of the variable power driving means, a reduction in cost, and a reduction in drive loss. Varifocal lens control that instantly corrects the image formation position shift peculiar to varifocal lenses and virtually maintains the in-focus state even when the overall focal length is updated by moving from one focal length to a second focal length. equipment can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the varifocal lens control device according to the present invention, and FIG. 2 shows the focal length f to be set, which is a characteristic of the varifocal lens used in the present invention. FIG. 3 is a diagram showing the changes and how each lens group moves, and FIG. 3 is a vertical sectional side view showing the specific configuration of the variable power drive section 4 and focus drive section 5 of FIG. 1, which are the main parts of the present invention. Figures 4 to 8 are enlarged views of each part of Figure 3, of which Figure 4 is a plan view showing the cam shapes and relationships between the linear cam groove of the fixed cell and the variable power cell. 5(a) is an enlarged plan view showing the connecting portion between the variable power cell and the variable power transmission cell, and FIG. 5(b) is the plan view shown in FIG. 5(a).
), FIG. 6 is a plan view showing the cam shapes and relationships between the fixed cell and variable power transmission cell, and FIG. 7 is a sectional view showing the cam shape and optical axis of the focus cell. FIG. 8 is a plan view showing the cam shapes of the focus cell fixed cell and the variable power transmission cell. DESCRIPTION OF SYMBOLS 1... Optical axis, 2... Variable power lens group, 2a to 2e... 1st group to 5th group lens, 3.
... Film surface, 4 ... Variable magnification drive section, 5 ... Focus drive section. 6... Focus counter 7... Combined lens group position detector (FPM), 8...
...Focal length detector (ZPM), 9...
Maximum feed amount calculation unit, 10...Proportional constant calculation unit 11...Focus correction calculation unit, 12...Focus control unit, 13...Magnification increase switch (up switch), 14...magnification down switch (down switch), 15... drive direction determination unit, 16... magnification change control unit. Mz, 45...Magnification variable motor, MF, 44...Focus motor, 10V...
...Power supply, 17...First group cell, 1
8-20...3rd group cell-5th group cell, 21.
...1st pin, 22-24...3rd pin - 5th pin, 25...
... Fixed cell, 26 ... First half, 27
...Second half, 28-31,41...Fixed cell linear cam groove,
32...variable magnification cell, 33a...
Gear part, 33b... Rotation transmission pin, 34... Variable power transmission cell, 34a...
Notch part, 35...Fixing part, 36.42...Cam groove of variable power transmission cell, 37~
39... Cam groove of variable power cell, 40...
Focus transfer cell. 40a, 40b... Focus pin, 43.
...Focus cell, 43b...Focus cell cam groove. Patent applicant Rico Co., Ltd. Agent Patent Attorney Makoto FB (II, 2J-W) Figure 4 Figure 5 (b) Figure 6

Claims (1)

[Claims] (1) The above-mentioned optical axis corresponds to the subject distance from close range to infinity when the focusing lens group of a variable power optical system is composed of a variable power lens group and a focusing lens group arranged on the same optical axis. After performing a focusing operation to set the focal point between the close position above and the infinity position, the variable magnification lens group adjusts the overall focal length of the variable magnification optical system to the shortest focal length and maximum focal length. In a varifocal lens that causes an image formation position shift for the same subject due to a magnification change operation that updates an arbitrary first focal length to a second focal length between The zoom lens group is made up of a plurality of lens groups that move in the direction, and the focusing lens group is made up of at least two lenses that move in the optical axis direction in conjunction with the focusing operation. Variable magnification lens group position detection that outputs position information corresponding to the position on the optical axis of the variable magnification component group consisting of the lens group and the remaining variable magnification lens group except for one lens group of this focusing lens group. a focusing lens group position detecting means for outputting position information corresponding to a position of the focusing lens group on the optical axis; a variable power driving means for driving the variable power component group; and a focusing lens group. a focusing drive means for driving the zoom lens group position detecting means and the focusing lens group position detecting means, respectively, to control starting and stopping of the zoom lens group position detecting means, and to control start and stop of the zoom lens group position detecting means, and to control start and stop of the zoom lens group position detecting means, and zooming focus correction control means for controlling the focus drive means to calculate a correction amount to correct the image formation position deviation and drive the focus lens group to the focus position. A varifocal lens control device featuring: