JP2565341B2 - Varifocal lens controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a varifocal lens control device, and more specifically, to a variable power lens unit and a focusing lens unit disposed on the same optical axis. In an optical system, the present invention relates to a varifocal lens control device in which the relationship between the subject distance and the amount of extension of the focusing lens group in the optical axis direction differs depending on the magnification position within the variable power range.

(B) Conventional technology Focusing of a zoom lens (focusing operation)
Is performed by moving a focusing lens group disposed in a part of the variable power optical system. Further, 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 “equal amount movement”). It is only necessary to attach the distance scale to the moving member (distance ring) of the focusing lens group and attach the index to the fixed ring arranged adjacent to this, and it is not necessary to change the subject distance scale according to zooming. There is an advantage that it does not. However, in the inner focusing type and rear focusing type zoom lenses, when the optical design is performed under the condition that the above-mentioned equal movement is realized, the lens configuration becomes complicated, though it depends on the lens configuration of the variable power optical system. There was a problem of doing. Further, there is a problem that the moving amount (extending amount) of the focusing lens unit on the wide angle side becomes unnecessarily large. Further, due to this, the outer diameter of the lens is increased, and the weight of the lens and the lens barrel is increased.

Therefore, in order to solve these problems, a varifocal lens that does not satisfy the above conditions for equal movement has already been proposed.However, this varifocal lens has a variable magnification corresponding to the zooming operation of the zoom lens described above. When the operation is performed, there is a problem that an image forming position shift occurs. In order to solve this problem, a part of the variable power optical system constituting the varifocal lens is used as a focusing lens group so that focusing drive independent of the variable power operation can be performed, and the variable power operation can be performed. Image position shift due to (may be referred to as "shift" below)
Is calculated, and the focusing lens group position is corrected based on the calculation result, it is considered that substantially the same operability as that of the zoom lens can be obtained.

Now, in the case where the shift correction is automatically performed in this way, for example, in order to set an arbitrary focal length, a variable magnification drive unit that drives the variable magnification optical system by a variable magnification motor or the like, and the focusing lens group is focused. A focusing drive unit driven by a motor, etc., a focal length detection base such as a potentiometer that detects the currently set focal length as an analog amount such as voltage, and the current position of the focusing lens group as an analog amount such as voltage. A control system is composed of, for example, a focus position detector such as a potentiometer for detection. In the varifocal lens, the focusing position of the focusing lens group with respect to the same subject changes depending on the focal length, and the locus of this change is a hyperbola whose variable is the focal length (output of the focal length detector). Now, if the focusing lens group is at the focusing position and the zooming operation is performed from this state, the control system of the varifocal lens moves the focusing lens group along the hyperbola to bring it into the focused state. However, for example, a focusing operation for correcting a change in the angle of view in the viewfinder to a natural one (hereinafter referred to as "shift correction operation").
That is) and the zooming operation for changing the focal length are alternately repeated until the focal length to be set is reached. In this way, every time the shift correction operation which is repeated alternately is performed, it is necessary to calculate the next extension amount and the driving direction of the focusing lens group up to the in-focus position.

On the other hand, in the camera body, automation of camera operation is advanced, and a microcomputer is often used in order to comprehensively and efficiently control these various complicated automatic operations. In other words, in a camera using a microcomputer, not only the center of control but also its periphery are digitalized. For example, the distance measurement data output from the distance measurement unit, which is the main part of the automatic focusing device, is also digital. Has been converted.
Therefore, it is of course possible to provide the automatic focusing device on the varifocal lens itself, but it is economically advantageous to share the automatic focusing device already built in the camera. Therefore, when sharing the existing automatic focusing device like this, in order to facilitate the interface between the taking lens and the camera body, the analog output of the focus position detector and the focal length detector is A / D converted. Must. However, this A / D converter has a slight conversion error (internal calculation error), and even if the lens groups corresponding to the detectors are stationary on the optical axis, The output of the A / D converter is constantly increasing / decreasing (changing). In other words, due to the position detection error of the variable power lens group and the focusing lens group, the calculation error when calculating the above-mentioned amount of extension, the shift control error, etc., the drive direction calculated with the amount of extension as described above is the corrected focus. There is a problem that it is output as an erroneous calculation result in the direction opposite to the direction to the position. Therefore, for example, if the drive direction is output correctly or is output in the wrong reverse direction, the focusing lens group vibrates, resulting in wasteful consumption of battery and power by the focus motor. Or, it causes adverse effects such as unnecessary wear of the members forming the focusing drive unit.

(C) Object The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a low-cost and simple structure, and to quickly perform a crystal position shift caused by a variable power operation peculiar to a varifocal lens at a high speed. It is an object of the present invention to provide a varifocal lens control device that can not only perform stable correction but also prevent wasteful consumption of power and unnecessary consumption of members.

(D) Configuration In order to achieve the above-mentioned object, the present invention is a variable power optical system including a variable power lens group and a focusing lens group arranged on the same optical axis. Is a varifocal lens having a relationship with the amount of extension in the optical axis direction that varies depending on the magnification position within the variable power range, and is a variable focal length that changes from an arbitrary first focal length within the variable power range to an arbitrary second focal length. In a varifocal lens control device that corrects an image forming position shift caused by a magnification operation by moving a focusing lens unit, a variable magnification driving unit that drives the variable magnification lens unit and a focusing unit that drives the focusing lens unit. Drive means, magnification change control means for controlling the magnification change drive means, and lens group position detection means for detecting the position of each lens group on the optical axis of the magnification change lens group and the focusing lens group. , This lens group position detection hand Total focus correction calculation means for receiving the focal length information and the focus lens group position information output from the focus lens group position information and calculating the movement amount and the driving direction of the focus lens group as the correction amount and the correction focus direction, respectively. An externally operable variable magnification direction indicating means for instructing a variable magnification direction to the variable magnification drive means, and a direction of the variable magnification operation instructed by the variable magnification direction instruction means are converted into a drive direction of the focusing drive means. Only when the driving direction coincides with the corrected focusing direction obtained by the focusing correction calculating means, the focusing driving means is controlled to drive the focusing lens group based on the correction amount. It is characterized in that it is provided with a focus control means, and is configured so as to stably and stably correct an image-forming position shift caused by the above-mentioned zooming operation.

Further, the position control of the focusing lens group by the focusing control means is performed every time the output of the zoom lens group position detection means changes by a predetermined amount from the start of the zooming operation.

Further, the present invention is characterized in that it is configured such that variable-magnification driving is performed concurrently during focusing correction driving.

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

FIG. 1 is a block diagram showing a configuration of an embodiment of a varifocal lens control device according to the present invention. In FIG. 1, reference numeral 1 is an optical axis of a variable power optical system, and 2 is a variable power lens group which is arranged on the optical axis 1 so as to be movable along the optical axis 1 and constitutes the variable power optical system. , 2a, 2b, 2c, 2d, and 2e are the first lens group consisting of a single lens or a plurality of lenses,
Second group lens, third group lens, fourth group lens and fifth group lens
It is a group lens. The fifth lens group 2e constitutes a focus lens group 3 as a focusing lens group.
The variable power lens group 2 includes the fifth lens group 2e, and the first lens group 2a to the fifth lens group 2e. The total focal length of the variable power optical system composed of the variable power lens group 2 is f, and Fm is the film surface. Reference numeral 4 indicates that the entire system focal length f is from the telephoto side focal length as the longest focal length (hereinafter simply referred to as "tele side") to the wide-angle side focal length as the shortest focal length (hereinafter simply referred to as "wide side"). A zooming drive unit 5 including a zooming motor Mz as a zooming driving unit for driving the zooming lens group 2 to set an arbitrary focal length up to 5 Infinity position on optical axis 1 corresponding to the subject distance (∞
The fifth lens group at the in-focus position from the position) to the closest position
2e, i.e. focus driver consisting focus motor M _F and a mechanism (not shown) of the focusing drive means for driving the focus lens group 3, 6 and 7 are driven by the focus drive unit 5 together with the focus lens group 3, respectively Of these, 6 is a focus counter for detecting the relative movement amount on the optical axis 1 of the focus lens group 3 which has generated a pulse proportional to the rotation number from the photo interrupter 6b when the slit disk 6a is rotationally driven,
Reference numeral 7 denotes a voltage proportional to the position of the focusing lens group 3 on the optical axis, and the focus position information as the focusing lens group position information.
A focusing lens group position detector (hereinafter abbreviated as "FPM") which forms a part of a lens group position detecting means for outputting as Sx;
Is driven by the variable power driving unit 4 together with the variable power lens unit 2 to output a voltage on the optical axis of the variable power lens unit 2 or a voltage proportional to the focal length f of the entire system as focal length information Zp.
A focal length detector (hereinafter abbreviated as "ZPM") that constitutes a lens group position detecting means together with the FPM7, 9 receives the focal length information Zp and performs A / D conversion, and then moves from the ∞ position to the closest position in this Zp. The maximum feed amount calculation unit for calculating the movement amount (that is, the feed amount) Fpm of the focus lens group 3 up to 10 and the output Fpm of the maximum feed amount calculation unit 9 and the focus position information of FPM7 (focus lens group position information) Output Sx as the output Sx and A / D-convert the output Sx to calculate the ratio thereof, and outputs a proportional constant Cfp, a proportional constant calculation unit, 11 receives the above three outputs Fpm, Cfp, Sx The focus correction calculation unit serves as a focus correction calculation unit that calculates a correction amount ± Dfp including a correction focus direction for focusing. The maximum feed amount calculation unit 9, the proportional constant calculation unit 10 and the focus correction calculation unit 11 constitute a total correction calculation unit 12 as a total focus correction calculation means. Therefore, this total correction calculation unit 12
The corrected focus position calculated by is the same as the above correction amount. Reference numeral 13 denotes a comparison / determination conversion unit serving as a focusing direction comparison / determination unit, which receives a variable-magnification direction signal (ZDR), which will be described later. And the corrected focus direction output from the focus correction calculation unit 11 (substantially the correction amount
Although it is the Dfp itself, for the sake of explanation, it is described as ± Dfp, and the sign of ± indicates the corrected focusing direction) and it is monitored whether or not the driving direction matches. If they match, the execution direction code (MD
R) is further output, and the correction amount Dfp is converted into a relative correction amount Drv which is a relative movement amount, and is output when it exceeds a predetermined value. The execution direction signal (MDR) is MDR = 1
To drive to the closest position side, and MDR = -1 to drive to the opposite ∞ position side. Therefore, in the correction focus direction (± Dfp), + Dfp means that the correction focus position is on the closest position side, and -Dfp means that the correction focus position is on the ∞ position side. The predetermined value is set to a value sufficiently larger than the error range of the A / D conversion conversion error and the calculation error in the total correction calculation unit 12. Reference numeral 14 is a distance measuring path that measures the distance to the subject and outputs a defocus amount Dfx as a relative amount corresponding to the number of rotations of the focus motor M _F to the planned focus position, and 15 is an output Dfc of the focus counter 6 and To receive the relative correction amount Drv or the defocus amount Dfx, respectively, and drive the focus lens group 3 to a corrected focus position corresponding to the relative correction amount Drv or a planned focus position corresponding to the defocus amount Dfx. Further, a focus control unit as a focus control unit for controlling the focus drive unit 5, 16 and 17 are variable power switches each including an externally operable push button switch for activating a variable power operation, and 16 is a magnification up switch ( Hereinafter, simply referred to as "up switch", 17 is a magnification down switch (hereinafter simply referred to as "down switch"), 18 is an output of these up and down switches 16 and 17. In response to the variable power motor Mz
Variable direction signal (ZDR) after determining the rotation direction of
A scaling direction determination section that outputs the
R) and the output Fpm, and is a magnification control section as a magnification control means for controlling the magnification drive section 4. The scaling switches 16 and 17 and the scaling direction determination unit 18 constitute scaling direction indicating means. Further, + V indicates a power supply, and the input / output relation of each part indicates only main signals. In addition, the scaling direction signal (ZDR) is a direction for increasing the magnification when ZDR = 1, that is, driving from the wide side to the tele side, and conversely, when MDR = −1, a direction for decreasing the magnification, that is, the variation from the tele side to the wide side. Instruct double drive.

In addition, the maximum feeding amount calculation unit 9 performs the focusing lens group 3 from the position ∞ to the closest position in the focal length information Zp.
Fpm = {C ₂ / (Zp + C ₁ )} + C ₃ (1), where Fpm is the maximum amount of extension and C ₁ , C ₂ , and C ₃ are the lens-specific constants of the variable power lens group 2, respectively. Is configured to run.

The constants C ₂ and C ₃ have the subject distance D as a parameter. Therefore this constant C _2, C ₃ is the closest object distance D ₀
Is included.

Further, the proportionality constant calculation unit 10 sets the output to Cfp, and sets the focus position information Sx immediately before performing the scaling operation and the maximum payout amount Fpm to S (i) and Fp (i), respectively, where Cfp = S ( i) / Fp (i) (2)

Further, the focus correction calculation unit 11 sets the output as Dfp, and sets the maximum feed amount corresponding to the focal length information Zp at the time of correction.
When Fpm is Fp (e), the operation Dfp = {Cfp · Fp (e) / 256} -S (i) (3) is executed.

The output Zp of ZPM8 is Zp = 255 on the tele side.
On the wide side, Zp = 0, while the FPM7 output Sx
Is configured such that Sx = 0 at the ∞ position and Sx = 255 at the closest position on the telephoto side.

FIG. 2 is a cam diagram showing respective movements in each mode of the variable power lens group 2 in FIG. 1 having a variable power mode, a macro mode, and a storage mode.

In FIG. 2, 20 to 24 are the first lens group 2a, respectively.
~ A cam line showing a locus when the fifth lens group 2e moves by a zooming operation, a macro operation and a retracting operation, particularly a cam line 24 shows a locus when the focus lens group 3 is at the ∞ position, and 24a also shows the same. A cam line of the fifth lens group 2e showing the locus when the focus lens group 3 is at the closest position, 25 is a tele position showing a position on the tele side, and 26 is a wide position showing a position on the wide side. 25a and 26a are a macro position and a storage position, respectively.

FIG. 3 is an enlarged development view showing a specific shape of a cam groove corresponding to the cam diagram of FIG.

In FIG. 3, reference numerals 27 to 31 denote cam grooves respectively corresponding to the cam lines 20 to 24 in FIG.
32 to 35 are formed on a fixed frame, and the first group lens 2
a, second lens group 2b, third lens group and fifth lens group 2
These are linear cam grooves for guiding c, 2e and the fourth lens group 2d in the optical axis direction. Incidentally, although 25 and 26 are the tele position and the wide position as described above, they are not actually on a straight line as shown in the cam diagram of the second illustration, so that they do not interfere with each other. The cam grooves 27 to 31 are appropriately offset in the circumferential direction. That is, the tele position 25 and the wide position 26 in FIG. 2 are equivalently shown.

FIG. 4 is a diagram for explaining the principle of calculation and the like of the comprehensive correction calculation unit in the embodiment shown in FIG.

In FIG. 4, the total focal length f to be set and the extension amount (movement amount) corresponding to the subject distance D of the focus lens group 3 are shown for each representative subject distance D, and the vertical axis represents the total system focal length. The abscissa indicates the amount of extension of the focus lens group 3 with respect to the focus position with respect to infinity. In this example, the tele position is f = 135 mm, and the wide position is f = 35 mm. Numerals 36 to 38 denote focusing curves when the subject distance D is ,, 3.0 m and the closest distance (1.2 m), respectively. As described above, the subject distance which is a parameter of the constants C ₂ and C ₃ of the equation (1) It is obtained by setting D to ∞, 3.0 m, 1.2 m, and becomes a hyperbola indicating a change in the amount of extension of the focus lens group 3 from the infinity position to the in-focus position with respect to a change in the focal length information Zp. Therefore, the focusing curve 38 is the closest focusing curve that provides the maximum amount of extension, and in particular, the amount of movement from the focusing curve 36 to the closest focusing curve 38 is the above-described maximum amount of delivery Fpm. Zp (i), S (i) and Fp (i) are the focal length information (first focal length information) Zp, the focus position information Sx and the Zp immediately before the zoom operation, respectively.
It is the movement amount Fpm (maximum amount of extension) from the infinity focusing curve 36 to the closest focusing curve 38 in (i), and Zp (e),
Fp (e) and Dfp are obtained from the focal length information (second focal length information) at the time when correction is required after the zooming drive unit 4 starts operation, and the focusing curve 36 in Zp (e). This is a correction amount for correcting the movement amount up to the focusing curve 38 and the focus movement.

That is, the ratio between Zp immediately before the zooming operation, that is, the ratio between the maximum feeding amount Fp (i) on Zp = Zp (i) and the feeding amount S (i) up to the current position of the focus lens group 3 is calculated by the above (2). Zp after the end of the scaling operation, that is, Zp = Zp (e)
In the above, if the focus lens group 3 is stationary due to the zooming operation (when the focusing operation is not performed during the zooming operation), S (i) is the same as S (i), and Fp (e )
Can be obtained by substituting Zp (e) into equation (1).
That is, since Dfp is an unknown number on Zp = Zp (e), using the proportionality constant Cfp obtained by the expression (2), the unknown Dfp is obtained by the expression (3). This Dfp is the correction amount, and if a sign is added, it becomes + Dfp in this case. Therefore, although the correction amount Dfp is shown large in FIG. 4 for the sake of easy understanding, the total correction calculation unit 1 including the conversion error due to the A / D conversion is described as described in the section of the prior art.
In the case of Dfp having a size that falls within the range of the calculation error in 2, the case where the opposite corrected focusing direction is output may occur. For example,
If the variable power lens group 2 and the focusing lens group 3 are stationary and the true correction amount is Dfp = 2, and the incorrect correction amount obtained as the calculation result is Dfp = 1, the correction at this time is performed. The focusing direction is -Dfp, and conversely, the correction amount obtained by the calculation is incorrect Dfp. That is, within the above calculation error range, + Dfp and −Dfp are randomly output as the correction focus directions, and if the focus lens group 3 is directly driven by this output, the focus lens group 3 vibrates already. As described in section.

FIG. 5 is a graph for explaining the operation of the embodiment shown in FIG. 1, and the same parts as those in FIG. 4 are denoted by the same reference numerals.

In FIG. 5, 38a and 39 are points intersecting the focusing curves 37 and 38 on Zp = Zp ₁ , respectively, and 40, 42 and 44 are the amount of change and the direction of the focal length information Zp in the magnification increasing operation. Arrows, S ₁ is the value of the focus position information Sx of the point 39, 41 and 41a are points intersecting the virtual straight line Sx = S ₁ on Zp = Zp ′ and the focusing curve 37, and 41b, 43, 45 are magnifications. In the up operation, arrows indicating the amount of change in the focus position information Sx and its direction, 46 and 46a are points at which the focus curves 37 and 38 on Zp = Zp ₃ are crossed, and 47 and 49 are in the magnification down operation. Arrows indicating the change amount of Zp and the direction thereof, and 48 and 50 are broken line arrows indicating the change amount of the focus position information Sx and the direction thereof in the same magnification down operation. Note that arrow 4
Both 3,48 are parallel on Zp = Zp ₂ . Reference numeral 41c is an arrow indicating an incorrect correction focus direction.

6 and 7 are flow charts showing the operation sequence of the embodiment shown in FIG. The configuration of this flowchart will be omitted here because it will be described together with the operation description below.

Now, the operation of the present embodiment configured as described above will be described. First, prior to the description of the variable-magnification operation, which is the main part, and the shift correction operation for correcting the focus movement associated with this variable-magnification operation, an automatic focusing operation in a general automatic focusing apparatus will be described. Focus lens group 3 now as the initial position
Is at the closest position, for example. Also, the subject distance D
Is D = 3.0m. If the distance measuring switch that activates the distance measuring operation or the release switch that activates the photographing operation (neither is shown) is operated, the distance measuring unit 14
Starts operation, and measures the distance to a subject (not shown). Then, outputs the measurement result as a defocus amount Dfx in terms of rotational speed of the focus motor M _F, the focus control section 15 having received the monitor output Dfc focus counter 6 rotates the focus motor M _F and, it is determined that the focus position stops the focus motor M _F with position became Dfc = Dfx. According to FIG. 5, the focusing lens group 3 is set on the focusing curve 37 of 3.0 m. That is, the focus lens group 3 has moved from the point 38a to the point 39 in FIG.

By the way, next about the scaling operation and the shift correction operation,
This will be described with reference to the flowcharts of FIGS. 6 and 7. It is now assumed that the focus lens group 3 is in a position where the subject at 3.0 m is in focus as described above. Therefore, it is on the focusing curve 37 in FIG.

First, the magnification increasing operation for shifting from the wide side to the tele side will be described. When the up switch 16 shown in FIG. 1 is pressed, the variable power direction determining unit 18 is activated, and the flowchart starts from START in FIG. That is, first, the variable-magnification direction determination unit 18 checks the state of the up switch 16 in the conditional branch of “magnification increase?”. In the present case, branch to YES, but if it branches to NO, check the status of the down switch 17 with the next conditional branch "Multiplier down?". If this down switch 17 is not operated, branch to NO. Then, the process returns to the conditional branching of "magnification increase?" Again, and the same operation is repeated until one of the magnification switches 16 and 17 is operated. Here, this operation loop is referred to as a “switch check loop”. Now,
In the next "ZDR = 1", the magnification change direction determination unit 18 outputs ZDR = 1 indicating this as a magnification change direction signal (ZDR) to the magnification change control unit 19 because the magnification change direction is the direction of increasing the magnification. Then `` Zp
In "read" and "Sx read", the maximum feed amount calculation unit 9 receives the output (Zp) as the focal length information of ZPM8.
A / D conversion is performed, and the proportional constant calculation unit 10 receives the output (Sx) as the focusing lens group position information of the FPM 7 and A / D converts the converted output, for example, Zp ₁ and Sp shown in FIG. 5, respectively. _Suppose it was ₁ . That is, it is assumed that the variable power lens group 2 is located at the point 39. In the next "calculation of maximum payout amount", the maximum payout amount calculation unit 9 substitutes Zp ₁ into the above equation (1) to calculate the maximum payout amount Fpm.
Is calculated.

In the next “calculation of proportionality constant”, the proportionality constant calculation unit 10 receives the maximum feed amount Fpm and calculates the proportionality constant Cfp according to the equation (2). That is, the S ₁ and S ₁ = S (i), the Zp ₁
Is set to Fpm = Fp (i), and these are substituted into the equation (2) to obtain Cfp. In other words, if it corresponds to FIG.
The ratio of the length from the in-focus curve 36 to the point 39 on Zp = Zp ₁ to the length from the in-focus curve 36 to the point 38a is obtained. The flow chart of FIG. 6 reaches the step of FIG. The operation up to and after the "switch check loop" will be referred to as "initial setting operation".

In the conditional branch “Continue scaling?” In the flowchart of FIG. 7, the scaling direction determination unit 18 uses the up / down switch.
Check whether 16/17 is pressed (ON state). Now, it is assumed that the up switch 16 is continuously pressed (hereinafter, this state is maintained until otherwise specified). Therefore, branch to YES in the above conditional branch,
In the next "magnification lens group drive", the magnification controller 19 rotates the magnification motor Mz in the magnification increasing direction with reference to the magnification direction ZDR = 1. That is, the scaling operation is started. Then, the zoom lens group 2 moves, and the output (Zp) of ZPM8 is also indicated by the arrow.
It changes as shown in 40. However, since the focus motor M _F is not operating in the FPM 7, the fifth lens group 2e changes (moves) according to the cam line 24 in FIG. 2 or the cam groove 31 in FIG. Is held at a fixed position and does not change due to the zooming operation. In the next "maximum payout amount calculation", the maximum payout amount calculation unit 9 reads the latest value Zp '(the position of the point 41) of the focal length information Zp that has begun to change in the direction shown by the arrow 40 in FIG.
As described above, the Zp ′ is substituted into the equation (1) to obtain the latest Fpm.
Is calculated. In the next "correction amount calculation", Sx is read again by the focus correction operation unit 11 in consideration of the rounding error of the A / D converter, mechanical play, etc., and the "proportional constant calculation" of FIG. 6 is performed. Using the proportional constant Cfp obtained in step S1, the Fpm corresponding to Zp ′ is Fp (e), and the read Sx is Sx = S ₁ = S
As (i), these are substituted into the equation (3) to calculate the correction amount Dfp.

The direction determining operation, which is the main part of the present invention, will be described below. In the next conditional branch “Is the sign correct?”, The comparison / judgment conversion unit 13
Determines whether the close-up side is the infinity side, but before that, a predetermined relationship that arises from the characteristics of the varifocal lens, that is, the variable power lens group 2, will be described.
As can be seen from the figure (especially focusing curves 37 and 38), when the magnification is instructed by ZDR = 1, the focusing curve 3
The correction focus direction to reach 7 or 38 is always the drive direction to the closest position side (MDR = 1), and when the magnification is instructed by ZDR = -1, it is indicated by MDR = -1. If it is driven to the ∞ position, the focus curve that is the corrected focus position is inevitable.
It has a relationship of reaching 37 or 38. In other words, if ZDR = 1, then MDR = 1 and vice versa.
If it is 1, then MDR = -1. Now, returning to the flowchart (FIG. 7), assuming that there is no rounding error of the A / D converter and no calculation error by the focus correction calculation unit 11 or the like, + Dfp corresponding to the arrow 41b is set as the correction amount including the correction focus direction. The received comparison determination conversion unit 13 branches to YES because the sign of the correction amount (+ Dfp) is positive in the above “sign is positive?”. Then, in the next conditional branch “magnification increase?”, It branches to YES by referring to the scaling direction signal MDR = 1 output from the scaling direction determination unit 18, and the next “MDR =
In the case of "1", as described above, the zooming direction is the direction of increasing the magnification and is the direction of the arrow 40 in FIG. 5, so in order to focus the focus lens in the direction of the arrow 41b approaching the focusing curve 37. It is determined that the group 3 should be driven, and the correction focus direction is set.
Determined that MDR = 1 (but not yet output).
In addition, the above "sign is correct?", "Magnification increase?", "MDR =
1 ”and“ Magnification down? ”And“ MD
Hereinafter, “R = −1” is collectively referred to as “direction determination operation”.

By the way, when the correct correction amount (+ Dfp) is not output as described above and the incorrect correction amount (-Dfp) indicated by the arrow 41c is output due to a calculation error or the like, the above "sign is correct?" The flow branches to NO, and the next conditional branch “magnification down?” Is also ZDR = 1, so the flow branches to NO and returns to the above “Continue scaling?” Again. The same operation is repeated until the correct direction is determined, that is, the correct correction amount (+ Dfp in this case) is output. Therefore, the direction check loop is an operation loop that branches from "Continuing scaling?" To "No scaling down?" Or "Up scaling?" In the direction determination operation to NO and returning to "Continue scaling?" Again. Call. Now, when MDR = 1 is determined, and in the next “conversion into movement amount”, the comparison and determination conversion unit 13 sets Ct as a constant determined by the specific configurations of the focus counter 6 and the focus drive unit 5, Drv = Dfp × Ct conversion is performed and the correction amount is
Dfp is converted into a relative correction amount Drv corresponding to the rotation speed of the focus motor M _F. Then, in the next conditional branch “Major focus deviation?”, The comparison and determination conversion unit 13 checks whether or not the relative correction amount Drv exceeds a predetermined value (for example, Drv ≧ 20), and moves the focus (shifts) by the zooming operation. (Amount) has become larger than a predetermined amount. And in this case, the variable magnification lens group 2 is still driven, so the shift amount (corresponding to the length between the points 41 and 41a in FIG. 5)
Is also small, branch to NO and return to "Continue scaling?"
Hereinafter, the above operation is repeated. Incidentally, here, this operation loop will be referred to as a "shift amount monitoring loop". Therefore, the shift amount monitoring loop and the direction check loop partially overlap. The variable power motor Mz continues to rotate, and the variable power lens group 2 is driven in the direction of the arrow 42 in FIG. When Drp = 20 is reached when Zp = Zp ₂ , the correction amount (+ Dfp) has already become a large amount (corresponding to the length of arrow 43) of the above-mentioned calculation error range in the above direction determination operation. Therefore, the correction focus direction MDR = 1 is determined as described above without outputting an erroneous correction amount (for example, -Dfp). Further, in the shift amount monitoring loop, "a large focus deviation?"
To YES, the comparison / determination conversion unit 13 sets the relative correction amount Drv and the correction focus direction MDR = 1 to the execution direction (MD
Output as R). And at the next "Variable drive stop",
The scaling control unit 19 stops the scaling motor Mz, and the focus control unit 15 which receives the relative correction amount Drv and the execution direction signal MDR = 1 rotates the focus motor M _F in the next “focus drive”. , The focus lens group 3 is driven to the close side, that is, in the direction of arrow 43 in FIG. In FIG. 2, it corresponds to the direction from the cam line 24 toward the cam line 24a. In the next conditional branch “correction in-focus position?”, The focus control unit 15 compares the output Dfc of the focus counter 6 with the relative correction amount Drv at once, and NO until the two match.
Then, the process returns to the “focus drive” described above, and the drive of the focus lens group 3 is continued. Then, when the focus lens group 3 moves in the direction of the arrow 43 shown in FIG. 5 and reaches the focus curve 37 of 3.0 m, Dfc = Drv, so the above conditional branch is branched to YES, and "Stop focus drive"
Stop the focus motor M _F with. The operation up to this point is the first cycle of the scaling operation and the shift correction operation, and the flowchart of FIG. 7 returns to "Continuing scaling?" And shifts to the control of the second cycle. Note that the operations from the “stop of variable magnification drive” to the “stop of focus drive” after the “shift amount monitoring loop” will be referred to as “correction focusing operation” here.

In the operation of the second cycle, the erroneous correction amount (-Dfp) is removed by the direction determining operation, and the zoom lens group 2 is driven in the direction of arrow 44 by the operation of the "shift amount monitoring loop". When the shift amount in Zp = Zp ₃ reaches a predetermined value moves to the correction focusing operation. If the up switch 16 is turned off during the correction focusing operation, the correction focusing operation is continued and the arrow mark
The focus lens group 3 is driven in the 45 direction. After that, the focus lens group 3 reaches the focusing curve 37 (point
(Position 46) Each part finishes the above correction focusing operation and returns to the conditional branch "Continue zooming?"
The variable power direction deciding unit 18 detects that it is F, and the flow chart branches to NO to proceed to the next subroutine "correction focus operation". The operation content of this subroutine is the same as the above-described correction focusing operation. However, in this case, the “variable magnification driving stop” has already been executed, the variable magnification motor Mz is stopped, and Drv = 0 immediately after the shift amount is also corrected. In, virtually nothing is done. That is, this subroutine is prepared for the case where the up / down switch 16/17 is turned off during the operation of the shift amount monitoring loop. The flow chart of FIG. 7 leads to
Moving to the figure, the above "switch check loop" is entered. Since the up / down switches 16/17 at present are not pressed, the operation of the "switch check loop" is repeated thereafter. This is the end of the magnification increasing operation.

Now, the variable power lens group 2 and the focus lens group 3 are present at point 46 in FIG. 5, and the operation of magnification reduction from here will be described. However, since it can be analogized from the above magnification increase operation, only the essential points are simplified. Explained.

Now, assuming that the down switch 17 has been pressed, "Zoom down?" Is branched to YES in the "switch check loop" of the flowchart in FIG. 6, and "ZDR = -1" indicates that the zooming direction is the zoom down direction. ZDR = -meaning that there is
1 signal is output, then the initial setting operation is performed, the variable magnification operation is started by moving to FIG. 7, and the wrong correction amount (+ Dfp in this case) is removed by the direction determining operation. The corrected focus direction MDR = -1 is determined. Thereafter, the shift amount monitoring loop and the correction focusing operation are executed. In FIG. 5, the variable power lens group 2 moves from the point 46 in the direction of the arrow 47, and when the shift amount exceeds a predetermined value, the correction focusing operation starts, and the focus lens group 3 is driven in the direction of the arrow 48. Then, the first cycle ends, and thereafter, the operation moves in the same manner as arrow 49 and arrow 50, and when the down switch 17 is turned off, this operation is stopped.

As described above, according to the present embodiment, when correcting the image forming position shift caused by the zooming operation, the zooming lens group 2 has a characteristic that the zooming direction signal (ZDR) indicating the direction of the zooming operation is provided. Focus lens group 2 according to a predetermined relationship that arises from
Of the correction amount (± Dfp) that includes the incorrect correction focus direction output from the total correction calculation unit 12 and is only the correction focus direction that matches the drive direction. Since the shift correction) operation is executed, it is possible to remove the correction amount (± Dfp) including an incorrect correction focus direction, and therefore, the focusing lens group 2 does not vibrate, and as a result, The advantages are not only that stable shift correction and variable-magnification operation can be performed at high speed, but also that power consumption by the focus motor M _F is not wasted, and unnecessary consumption of the members forming the focus drive unit 5 can be prevented.

Further, since the shift correction is executed only when the relative correction amount Drv exceeds a predetermined value which is sufficiently larger than the fluctuation component such as the calculation error, there is an advantage that more stable control can be performed.

Further, the correction amount Dfp calculated as an absolute amount is converted into a relative correction amount Drv that can be compared with the count number of the focus counter 6 corresponding to the rotation angle (pulse number) of the focus motor M _F , and the position of the focus lens group 3 is converted. Since it is configured so as to control, the resolution is remarkably higher than that in the case where a potentiometer such as FPM7 is used as the relative movement amount detecting means, so that there is an advantage that highly accurate position control can be realized. Further, the comparison / determination conversion unit 13 sets the correction amount Dfp to
Since it is configured to convert to a relative correction amount Drv that is the same relative amount (digital amount) as the defocus amount Dfx output from the distance measuring unit 14 of the automatic focusing device built into the camera, the shift correction is performed. , A part of the automatic focusing device originally built in the camera, that is, the focus counter 6, the focus motor M _F , the focus control unit 15, and the like can be shared for the shift correction of the varifocal lens, and they are shared. The configuration can be simplified by the amount corresponding to the above, and the cost can be reduced.

The present invention is not limited to the above-mentioned embodiment,
Various modifications can be made without departing from the spirit of the invention.

For example, the variable power switches 16 and 17 may not be composed of two switches, the up switch 16 and the down switch 17, but may be composed of a single switch if the variable power direction determination unit has a memory function. In addition, the determination of "large focus deviation?" In the flowchart shown in FIG. 7 is not limited to Drv ≧ 20, and is selected so that control speed and control stability, finder observation image appearance, etc. are optimized. In that case, the numerical value may be increased or decreased, and the shift correction may be performed for each fixed amount of magnification change.

Further, during the correction focusing operation, the variable power drive may be concurrently performed without stopping the variable power drive as long as the power sources of the motors M _F and Mz are not adversely affected.

Further, in the above-described embodiment, the automatic focusing device built in the camera is configured to receive the defocus amount signal from the distance measuring unit 14 so as to be able to perform automatic focusing. Needless to say, the present invention can be applied to a camera having no camera.

(E) Effects As described in detail above, according to the present invention, when correcting the image-forming position shift peculiar to the varifocal lens caused by the magnification changing operation, the direction of the magnification changing operation instructed by the magnification changing direction indicating means is set. After converting to the driving direction of the focusing lens group according to a predetermined relationship, the focusing lens group is changed based on the above correction amount only when this driving direction matches the corrected focusing direction obtained by the focusing correction calculation means. Since the focus control means is configured to drive and control the focus drive means for driving,
Although it is inexpensive and has a simple structure, it is possible to correct the image forming position deviation at a high speed and in a stable state without causing vibration of the focusing lens group, and at the same time, waste power consumption and focusing lens group It is possible to provide a varifocal lens control device that can prevent unnecessary wear of constituent members.

[Brief description of 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, and FIG. 2 is a cam diagram showing respective movements of the variable power optical system shown in FIG. 3, FIG. 3 is an expanded view showing an enlarged specific shape of a cam groove corresponding to this cam diagram, and FIG. 4 shows characteristics of the device of the present invention shown in FIG. 5 is a graph showing the relationship between the focal length f of the entire system to be set and the amount of extension Sx of the focus lens group corresponding to the subject distance D, for each subject distance, and FIG. A graph for explaining the operation of the embodiment shown in FIG. 1, FIGS. 6 and 7 are flowcharts showing the operation sequence of the embodiment shown in FIG. 1 ... Optical axis, 2 ... Variable magnification lens group, 2a to 2e ... 1st group lens to 5th group lens, 3 ... Focus lens group, Fm ... Film surface, 4 ... Variable magnification drive unit, 5 ... Focus drive unit, 6 ... Focus counter, 7 ... Focusing lens group position detector (FPM), 8 ... Focal length detector (ZPM), 9 ... Maximum extension amount calculation unit, 10 ... Proportional constant calculation unit, 11 ... Focus correction calculation unit, 12 ... Total correction calculation unit, 13 ... Comparison judgment conversion unit, 14 ... Distance measuring unit, 15 ... Focus control unit, 16 ... Magnification up switch (up switch), 17 ...... zoom switch (down switch), 18 ...... driving direction determination unit, 19 ...... magnification change control unit, Mz ...... zooming motor, M _F ...... focus motor.

Claims (3)

(57) [Claims] 1. A variable power optical system comprising a variable power lens group and a focusing lens group arranged on the same optical axis, wherein the relationship between the object distance and the amount of extension of the focusing lens group in the optical axis direction. , A varifocal lens that varies depending on the magnification position within the variable power range, and focuses an image position shift caused by a variable power operation that updates from an arbitrary first focal length within the variable power range to an arbitrary second focal length In a controller for a varifocal lens that corrects by moving a lens group, a zooming driving unit that drives the zooming lens unit, a focusing driving unit that drives the focusing lens unit, and a zooming driving unit are controlled. Zooming control means, a lens group position detecting means for detecting the position of each lens group on the optical axis of the zooming lens group and the focusing lens group, and output from this lens group position detecting means. Focal length information and focus General focus correction calculation means for receiving the lens group position information and calculating the moving amount and the driving direction of the focusing lens group as the correction amount and the corrected focusing direction, respectively, and the zooming direction with respect to the zooming driving means. An externally operable variable magnification direction instructing means for instructing and a direction of the variable magnification operation instructed by the variable magnification direction instructing means are converted into a drive direction of the focusing drive means, and then this drive direction and the in-focus state are set. Focusing control means for controlling the focusing driving means so as to drive the focusing lens group based on the correction amount only when the corrected focusing direction obtained by the correction calculation means matches. A varifocal lens control device characterized in that it is configured to correct an image forming position shift caused by a doubling operation at high speed and stably. 2. The position control of the focusing lens group by the focusing control means is performed each time the output of the zoom lens group position detection means changes by a predetermined amount from the start of the zooming operation. The varifocal lens control device according to claim 1. 3. The varifocal lens control device according to claim 1, wherein variable power driving is performed concurrently during focusing correction driving.