JPH0542411Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Technical field The present invention relates to a varifocal lens control device, and more specifically, to a variable focal lens control device consisting of a variable magnification lens group and a focusing lens group arranged on the same optical axis. After setting the focusing lens group of the magnification 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,
By updating the entire focal length of the variable magnification optical system by the variable magnification lens group from a first focal length to an arbitrary second focal length between the shortest focal length and the longest focal length, the same subject can be photographed. On the other hand, this relates to a varifocal lens that causes an image formation position shift.

(b) Prior Art A zoom lens does not shift the imaging position (so-called focus movement or focus shift) even when zooming is performed, so it is easy to operate without the hassle of adjusting the focus for each zooming operation. In addition, in recent years, with the advancement of cameras with AF, the inherent mobility of zoom lenses can now be demonstrated, and operators (users)
Now you can concentrate on deciding the composition according to your drawing intention, and the operability has been significantly improved.

Generally, focusing (focusing operation) of a zoom lens is performed by moving a focus lens group disposed as a part of a variable power optical system. The zoom lens has an advantage in that the amount of movement of the focus lens group is approximately the same for the same subject distance in the entire zoom range (hereinafter, this will be referred to as "equal amount movement").

By the way, although the operability of zoom lenses has improved by combining them with the AF function, it is impossible to escape from the above-mentioned condition of equal movement that zoom lenses have, so it is difficult to realize compactness and cost reduction. The problem of difficulty remained.

Therefore, in order to solve these problems, a varifocal lens, which is a simple optical system that does not meet the above-mentioned condition of equal displacement, has recently come to be used in place of a zoom lens. However, since the above-mentioned condition of equal movement is removed, the amount of movement of the focus lens group for the same subject differs between the long focus side and the short focus side, and control of the focus lens group is not as simple as in the case of a zoom lens. . Therefore, in order to change the focus lens group and focal length, a lens position detector is provided to detect the position of the variable power lens group on the optical axis, and based on the focus position information and variable power position information obtained from these, One possibility is to control the focusing lens group. A potentiometer is used as a lens position detector that can easily detect the absolute position with a simple configuration, and the voltage output from this potentiometer is used as the focus position information and magnification change position information. be able to. However, the potentiometer is basically a simple sliding resistor, and its output voltage may vary depending on the contact state of the slider. In other words, even if the focus lens group or the variable magnification lens group is stationary, a voltage that is larger than its true value or a voltage that is small may be output. Also,
In extreme cases, the slider may float away from the resistor, resulting in poor contact and an unstable potential. Especially when the focus lens group or variable power lens group is located at the end of its range of motion,
If the variable magnification lens group or the focus lens group is driven based on erroneous information due to the voltage fluctuations, a problem arises in that the lens collides with a stopper provided at the end of each lens group, becomes locked, and becomes uncontrollable.

(c) Purpose This invention was created in view of the above circumstances.
The purpose is to avoid complicating the configuration,
It is possible to prevent erroneous control of the focusing lens group based on erroneous focusing lens group position information and/or variable power lens group position information with a low cost and simple configuration without increasing costs. It is an object of the present invention to provide a varifocal lens control device that reliably prevents a focal lens group from becoming uncontrollable.

(d) Configuration In order to achieve the above-mentioned object, the present invention is designed to operate the focusing lens group of a variable power optical system consisting of a variable power lens group and a focusing lens group arranged on the same optical axis from a close distance. After setting the focus position on the optical axis from the closest position to the infinity position, which corresponds to the subject distance reaching infinity, the variable magnification lens group adjusts the overall focal length of the variable magnification optical system. 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 the shortest focal length and the longest focal length, the shortest focal length mentioned above The focal length at the infinity position remains unchanged with respect to a change in the focal length of the entire system from the maximum focal length to the maximum focal length, and the focal position at the close position changes so as to gradually move away from the infinity position. A focal lens, a focusing drive means for driving the focusing lens group, a variable power driving means for driving the variable magnification lens group, and a focusing lens that detects the position of the focusing lens group on the optical axis and focuses the lens. a focusing lens group position detection means that outputs lens group position information; and a variable power lens group that detects a position on the optical axis corresponding to the focal length of the variable power lens group and outputs variable power lens group position information. a position detection means, a maximum extension amount calculation means for receiving the variable power lens group position information and calculating an extension amount of the focusing lens group from the infinity position to the close position at the focal length; and the maximum extension amount. Receives and compares the calculation means and the focusing lens group position information, and determines whether or not the content of the focusing lens group position information exceeds the maximum extension amount, and exceeds the maximum extension amount. If the size is the same, the above-mentioned focusing lens group position information and/or the above-mentioned variable power lens group position information are considered unreliable, and the above judgment is made again, or after the above-mentioned variable power lens group is driven once, the above judgment is made again. The present invention is characterized in that it is comprised of lens position determination means for executing the lens position determination means.

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

FIG. 1 is a block diagram showing the overall configuration. In Figure 1, 1 is the optical axis of the variable magnification optical system, 2
is a variable magnification lens group that is movably disposed on the optical axis 1 and constitutes the variable magnification optical system, and 2a, 2b, 2c, 2d, and 2e are each singly or plurally arranged. The first group lens consists of lenses,
They are a second group lens, a third group lens, a fourth group lens, and a fifth group lens. And the first group lens 2a
The second lens group 2b constitutes a focus lens group as a focusing lens group.
The variable power lens group 2 includes the first group lens 2a, the second group lens 2b, and the third group lens 2c to the fifth group lens 2e. The total focal length of the variable magnification optical system is f
It is. 3 is the film surface, and 4 is the focal length f of the entire system.
is any focal length between the telephoto side focal length (hereinafter simply referred to as "tele side") as the longest focal length and the wide-angle side focal length (hereinafter simply referred to as "wide side") as the shortest focal length. 5 is an optical axis corresponding to the subject distance from _infinity to close-up. The first group lens 2a and the second group lens 2b are driven to a focusing position between an infinity position (∞ position) on A focus motor as a focusing drive means (moves in the direction of the optical axis while keeping the distance between 2b and 2b constant)
Focus drive units 6 and 7, each consisting of an M _F and a mechanical unit (not shown), are driven by the focus drive unit 5 together with the first group lens 2a and second group lens 2b, respectively. A focus counter that generates a pulse proportional to the rotational speed of the photointerrupter 6b by being rotationally driven and detects the amount of movement of the first group lens 2a and the second group lens 2b on the optical axis 1; is the focus position information _S
A focusing lens group position detector (hereinafter abbreviated as "FPM") 8 serves as a focusing lens group position detecting means for outputting a focusing lens group position, and 8 is driven by a variable power drive unit 4 together with a variable power lens group 2 to bring the entire system into focus. A variable power lens group position detector (hereinafter referred to as "ZPM") serves as a variable power lens group position detection means that outputs a voltage proportional to the distance f as focal length information _ZP as variable power lens group position information.
), 9 receives the focal length information Z _P via the buffer 9 a, converts it A/D, and then converts the information from the ∞ position to the closest position at Z _P to the first lens group 2 a and the second lens group. 10 is _a buffer for focus position information _S Output F _PX and output S _X as focus position information of FPM7 via buffer 10
Then _, the output S _X is _A / _D converted and compared, and when the focus position information _S Output (raise to H level),
Lens position determination units 9a and 10, which serve as lens position determination means for maintaining the L level when F _PX ≧S _X , are configured almost identically. Batsuhua 9
To explain a little using a as a representative, operational amplifier OP
The output terminal of ZPM8 is connected to the non-inverting input of , and is also connected to the power supply +V via a resistor R. However, the resistance R is much larger than the resistance value of ZPM8 or FPM7, and the output Z _P or
It is configured so as not to give an error to S _X. In addition, the output terminal of the operational amplifier OP is connected to the input terminal of the maximum payout amount calculating section 9 and also to its own inverting input terminal, forming a so-called buffer amplifier with an extremely high input impedance, although it does not have an amplification effect. There is. Therefore, even if there is poor contact between the slider of ZPM8 and the resistor, the output of ZPM8 will be
The potential of Z _P is not uncertain and is configured to be a potential of +V or a potential higher than the true value. 12 is the output Dfc of focus counter 6
and a focus control unit as a focus control unit that controls the focus drive unit 5 in response to the defect signal NG and the output Dfp corresponding to the correction amount of a focus correction calculation unit (not shown); 13 to 15 constitute starting means; , 13 and 14 are magnification change switches each consisting of an externally operable push button switch that starts the magnification change operation, 13 is a magnification up switch (hereinafter simply referred to as "up switch"), and 14 is a magnification down switch (hereinafter simply referred to as "down switch"). 15 is a drive direction determination unit that receives the outputs of these switches 13 and 14, determines the rotation direction of the variable magnification motor _MZ , and outputs a start signal STR;
16 is the above start signal STR and the above fault signal NG
This is a magnification control section as a magnification control means for controlling the magnification variable driving section 4 in response to the received power. In addition, +V indicates the power supply,
Also, the input/output relationship of each part shows only the main signals.

FIG. 2 is a graph showing the characteristics of the variable magnification optical system shown in FIG. The amount of movement (amount of movement) corresponding to the distance D is shown for each typical subject distance D,
The vertical axis shows the change in the focal length f of the entire system, and the horizontal axis shows the amount of extension of the focus lens group with reference to the in-focus position at infinity. In this example, the tele position is f=135mm, and the wide position is f=135mm.
=35mm. In Fig. 2, 17 to 22 are focusing curves, and the subject distance D is ∞, 6.0 m, and 6.0 m, respectively.
Focus lens group 2a, with respect to changes in focal length information _ZP when 3.0m, 2.0m, 1.5m, and 1.2m,
2b shows the change in the amount of extension from the infinity position to the in-focus position. Therefore, the focusing curve 22 is the closest focusing curve with the maximum amount of feeding, and the maximum feeding amount F _PX
is the same as

F _PX = C ₂ / Z _P + C ₁ + C ₃ (1) In the above, when subject distance D is substituted as a parameter into constants C ₂ and C ₃ , that is, C ₂₂ and C ₃₃
As new constants, C ₂ = C ₂₂ (D), C ₃ = C ₃₃ (D)
By setting, the focusing curves 17 to 22 are determined, and especially when the closest subject distance D ₀ is substituted,
A focusing curve 22 is determined.

FIG. 3 is a diagram for explaining the operation of the embodiment shown in FIG. 1, and the same parts as in FIG. 2 are given the same reference numerals.
Z _P = S _X on Z _P ( ₁ ) = S ₁ , S _X = S ₀ , S _X = S ₃ , S _X =
The points of intersection with S ₂ , especially the intersections 23 and 24, are located on the focusing curves 21 and 22. Also, at S∞=0,
The magnitude relationship is S∞<S ₄ <S ₁ <S ₂ <S ₀ <S ₃ .

27 and 28 are arrows indicating the driving direction of the focus lens groups 2a and 2b, 29 is the intersection of Z _P = Z _P ( ₂ ) and the focusing curve 21, and 30 is the direction in which the variable power lens group 2 is driven. The indicated arrow 31 is an arrow indicating the driving direction of the focus lens groups 2a and 2b.

FIGS. 4 and 5 are flowcharts showing the operation sequence of the embodiment shown in FIG. 1, and show the redetection mode and drive mode of the determination operation, respectively. Note that the configuration of the above flowchart will also be described in the operation description below, so it will be omitted here.

Now, the operation of this embodiment configured as described above will be explained. First, before explaining the above-mentioned determination operation, which is the main part of the present invention, a magnification changing operation for changing the focal length will be briefly explained. It is now assumed that the variable power lens group 2 and the focus lens groups 2a and 2b are located at the intersection 29 in FIG. 3 in a focused state. for example,
To explain the operation of increasing the magnification from the wide side to the telephoto side, when the up switch 13 shown in FIG. The magnification changing operation is started when the magnification changing control section 16 starts controlling the driving of the magnification changing lens group 2 in the direction of increasing the magnification. Then, the focus correction calculation unit (not shown ₎ calculates _S
1 is the direction of increasing the magnification after reading Z _P =Z _P ( ₂ ), respectively, so the variable magnification lens group 2 is driven by the variable magnification control unit 16 in the direction of the arrow 30 as described above. Ru. Then, after driving by a predetermined amount from Z _P = Z _P ( ₂ ) to Z _P = Z _P ( ₁ ), the driving of variable magnification lens group 2 is stopped in order to correct the focus shift caused by this driving. Here, the focus correction calculation section
S _X = S ₄ , and the maximum feed amount calculation unit 11 calculates Z _P = Z _P
( ₁ ) is read again, and the ratio between the maximum feed amount F _P ( ₂ ) calculated from the above Z _P ( ₂ ) and S ₄ and the Z _P ( ₁ ) that has just been read.
The above correction amount is calculated from the maximum feeding amount F _P ( ₁ ) calculated from
Dfp is calculated, and the focus control unit 12 that receives this correction amount Dfp drives the focus lens groups 2a and 2b in the direction of the arrow 31, and at the intersection 23 on the focusing curve 21, the output Dfc of the focus counter 6
Since the above-mentioned _DFP becomes equal, the focus lens groups 2a and 2b are stopped at this point, and one cycle of the zooming operation is completed. Thereafter, if the up switch 13 is operated, a second cycle is executed with the intersection 23 as the starting point, and thereafter the camera moves to the telephoto side in the same manner. In this zooming operation, the reading of Z _P and _S

Next, the operation of the main parts of the present invention will be explained. It is assumed that the variable power lens group 2 and the focus lens groups 2a and 2b are stopped in focus at a point 24 shown in FIG. In other words, it is assumed that the focus drive unit 5 and the variable power drive unit 4 are in contact with or are stopped at a position extremely close to a stopper that restricts the movement of the focus lens groups 2a, 2b at a close position. Here, it is assumed that the above-mentioned magnification changing operation is started. At this point, the flowcharts in Figures 4 and 5 are
It starts from START. First, the determination operation (redetection mode) will be explained along the flowchart of FIG. Note that in this re-detection mode, the defect signal NG from the lens position determining section 11 is not output. At the first “Z _P reading”, the maximum feeding amount calculation unit 9 is
Read Z _P = Z _P ( ₁ ) and calculate the maximum feeding amount F _PX using the formula (1) in "Maximum feeding amount calculation". According to FIG. 3, in this case F _PX =S ₀ . Then, in the next "S _X reading", the lens position determining section 11 reads the focus position information S _X via the buffer 10. However, here, S _X = S ₀ is supposed to be read as the focus position information, but due to a contact failure inside the FPM 7, S _X = S ₃ is output as the focus position information corresponding to point 25. .
At the next conditional branch "F _PX < S _X ?", the lens position determination unit 11 branches to _YES since F _PX < _S
Go back and repeat the same action. This operation loop is called a redetection loop. In general, contact failures that occur in the FPM7 and ZPM8 are often one-off or instantaneous, and while the above re-detection loop is continued several times, _a normal _S Ru. Now, when the correct focus position information S _X = S ₀ is received in this way, "F _PX < _S finish. and,
After this, the above magnification changing operation is executed. In addition, the above-mentioned "F _PX < _S
This may be a case where the focal length information Z _P for calculating the above-mentioned F _PX is incorrect, but since the concept of operation is the same as described above, the explanation will be omitted.

Now, following the flowchart in Figure 5,
The determination operation (drive mode), which is another important part, will be explained. It is assumed that the positions of each lens group are the same as in the re-detection mode described above. In other words, assume that it is at point 24. Here, it is assumed that the variable magnification operation is also started in the same way.
The flowchart starts from START at this point, and the steps from "Z _P read" to condition separation "F _PX > S _X ?" are the same as the redetection mode described above. Now, _S
When incorrect focus position information such as = _S3 is read, the lens position determination unit 11 determines "F _PX <S _X ?"
It branches to YES and raises the fault signal NGH level, and in response to this, the variable power control unit 10 rotates the variable power motor M _Z in the direction fi toward the telephoto side in the next "variable magnification fine movement" to control the variable magnification lens group. 2 and drives ZPM8. And also the above H level fault signal
After receiving the NG, the focus control unit 12 uses the next "focus micro-movement" to control the focus motor M _Z by, for example, ∞
Focus lens group 2 by rotating it toward the position side.
Drives FPM7 together with a and 2b. Then, return to the above-mentioned "Z _P reading" and repeat the same operation. This operation loop is called a drive redetection loop.
As mentioned in the explanation of the same re-detection mode, FPM7,
It is known from experience that ZPM8 contact failures are often one-off and instantaneous, and that a slight stimulus (movement) can restore the contact to a normal state. Therefore, the above-mentioned "fluctuation fine movement" and the above-mentioned "focus fine movement" are different from the original driving for the above-mentioned magnification changing operation in terms of short driving time.

Now, after continuing the drive re-detection loop several times, the contact failure is resolved, and the correct focus position information S _X = S ₀ is input via the button 10, so that the lens position determination section 11 In the drive re-detection loop, "F _PX < _S focus control section 12
Then, the variable magnification control unit 16 stops the respective motors M _F and M _Z , and completes all determination operations (drive mode) at the next END.

In this way, according to this embodiment, the focus position information _S
Alternatively, check the reliability of the focal length information Z _P , and if _it is determined that it is unreliable, read the focus position information _S ) and then reused, due to erroneous control based on erroneous information, the lens collides with the stop formed by the variable magnification drive section 4 and the focus drive section 5 and becomes locked. This has the advantage of preventing uncontrollable situations like this.

In the flowchart in Figure 5, the "variable magnification fine movement" is a drive toward the telephoto side, and the "focus fine movement" is a drive toward the ∞ side, so as can be seen from Figure 3, the amount of drive is minute. Since the drive is to the safe side away from the stopper, there is an advantage that it acts as a double safety mechanism against the locked state.

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, if a counter is configured to count in the re-detection loop and drive re-detection loop in Figs. 4 and 5, and the correct Z _P or S _X cannot be obtained even after counting a predetermined count value, , it may be configured to display a defective indication.

Furthermore, in the drive re-detection loop shown in Fig. 5, both the "variable magnification micro-movement" and "focus micro-movement" operations are not necessarily executed together, but only one of them may be executed, thereby still providing correct information. The configuration may be such that the other is executed only when the other is not available.

In addition, in the explanation of the operation shown in FIG. 4 and FIG.
Applicable to all operations that require reading Z _P or S _X. Therefore, the variable magnification operation may be applied not only to the first reading operation but also to the second reading operation.

In addition, in this embodiment, explanation was given only at a close position, but it is determined that Z _P and _S You can. In other words, it may be applied on the ∞ position side.

Further, the resistors R of the buffers 9a and 10 are not limited to passive elements, and may be formed of active elements such as transistors.

(e) Effects As detailed above, the present invention has the advantage of having a simple configuration, being able to be manufactured at low cost, being compact, and being lightweight; however, on the other hand, position information of the focusing lens group and the variable magnification lens group is required. In a varifocal lens, the maximum extension amount is calculated based on the position information on the optical axis corresponding to the focal length of the variable magnification lens group, and the maximum extension amount is calculated based on the position information on the optical axis corresponding to the focal length of the variable magnification lens group. It is determined whether the content of this position information exceeds the maximum dispensing amount, and if it exceeds the maximum dispensing amount, the above judgment is made again as both of the above position information are unreliable. Or, after the focusing lens group and/or the variable magnification lens are once driven, the above judgment is performed again, so it is very simple and can be manufactured at low cost, and the above position information that is erroneous can be corrected. To provide a varifocal lens control device capable of eliminating erroneous positional information, preventing erroneous control of a focusing lens group due to this erroneous position information, and reliably preventing the focusing lens group from becoming uncontrollable. I can do it.

[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 is a graph showing the characteristics of the variable magnification optical system shown in FIG. A graph showing the relationship between the total system focal length f and the focus lens group extension amount S _X corresponding to the subject distance D for each subject distance,
3 is a graph showing a part of the above-mentioned FIG. 2 to explain the operation of FIG. 1, and FIGS. 4 and 5 are flowcharts showing the operation order of FIG. 1, respectively. 4 shows the re-detection mode of the determination operation, and FIG. 5 shows the drive mode of the determination operation. 1... Optical axis, 2... Variable magnification lens group, 2a to 2e
...1st group to 5th group lens, 3...film surface,
4...Magnification variable drive unit, 5...Focus drive unit, 6
... Focus counter, 7 ... Combined lens group position detector (FPM), 8 ... Variable magnification lens group position detector (ZPM), 9 ... Maximum extension amount calculation section, 9a, 1
0... Buffer, 11... Lens position determination section, 1
2...Focus control unit, 13...Magnification up switch (up switch), 14...Magnification down switch (down switch), 15...Drive direction determination unit, 16...Magnification control unit, _MZ ...Magnification variable motor , M _F ...Focus motor, +V...Power supply.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A variable power optical system consisting of a variable power lens group and a focusing lens group arranged on the same optical axis, from a close range to an infinite distance. After setting the focus position between the closest position and the infinity position on the optical axis corresponding to the subject distance, the variable magnification lens group adjusts the overall focal length of the variable magnification optical system to the shortest and longest focal lengths. 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 the focal lengths, from the shortest focal length to the longest focal length. the varifocal lens in which the focal position at the infinity position remains unchanged and the focal position at the close position gradually moves away from the infinity position when the focal length of the entire system changes; A focusing driving means for driving the focusing lens group, a variable power driving means for driving the variable magnification lens group, and a focusing lens group detecting the position of the focusing lens group on the optical axis, a focusing lens group position detection means for outputting, a variable power lens group detection means for detecting a position on the optical axis corresponding to the focal length of the variable power lens group and outputting variable power lens group position information; maximum extension amount calculation means for receiving variable power lens group position information and calculating the extension amount of the focusing lens group from the infinity position to the close position at the focal length; the maximum extension amount calculation means and the focusing lens group; Receive each lens group position information and compare them to determine whether the content of the focusing lens group position information exceeds the maximum extension amount, and if the content exceeds the maximum extension amount, the above Lens position determining means for performing the above determination again or once driving the variable magnification lens group and then performing the determination again because the focusing lens group position information and/or the variable power lens group position information is unreliable; A varifocal lens control device comprising: (2) The maximum extension amount calculating means calculates the output corresponding to the extension amount from the infinite position to the closest position as F _PX , the output of the variable magnification lens group position detection means as Z _P , and a constant specific to the lens of the variable magnification optical system. The utility model registration claim described in claim 1 is characterized in that, when C ₁ , C ₂ , and C ₃ respectively, an operation is performed using the arithmetic formula F _PX = C ₂ /Z _P + C ₁ + C ₃ . Varifocal lens control device.