JP2672498B2 - Image correction device for zoom lens - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens, and more particularly to an image correction device for a zoom lens that corrects an image formation position that occurs during zooming operation in a front lens fixed zoom lens. 2. Description of the Related Art Conventionally, a so-called front lens fixed zoom lens having a focusing lens on the image side of a variable power lens is well known, and such a front lens fixed zoom lens needs to be moved for a focusing operation. Although it has the advantage that the lens can be made small and lightweight, or that it can focus on the subject at the closest point, on the other hand, it has the problem that the image-forming position, that is, the focal position, moves greatly due to the zooming operation. There is. On the other hand, it is needless to say that it is desired to perform the zooming operation while confirming the subject, that is, to maintain the in-focus state with respect to an arbitrary subject during the zooming operation. Therefore, in the case of the front fixed zoom lens as described above, some kind of correction means is required.
Means such as those disclosed in Japanese Laid-Open Patent Publication No. 66445 or Japanese Laid-Open Patent Publication No. 55-40447 are known. The former is based on obtaining the amount of movement of the focusing lens required for the above-described magnification varying operation based on the position of the magnification varying lens and the distance to the subject from a predetermined relational expression determined in advance by each lens, It discloses a mechanical method using a plurality of non-linear cams based on a relational expression or an electric method for driving the focusing lens by a driving source such as a motor by obtaining the movement amount by a calculation based on the relational expression. The latter detects the shift of the image forming position caused by the movement of the zoom lens by using the autofocus device, that is, treats the shift of the image forming position as if the distance information to the subject is changed. Disclosed is a means of performing a move. Problems to be Solved by the Invention The mechanical method in the former method is extremely expensive because a mechanism such as a non-linear cam requires complicated and high-precision machining, and the electrical method is a variable lens position, an object. position,
A structure for accurately detecting three types of focusing lens positions is required, and higher-order calculations must be performed. Considering the above-described detection structure and calculation element, the problem of becoming expensive and large-sized Have The latter means is not particularly problematic if the image plane shift due to the movement of the zoom lens is relatively small and the short focus side has a large depth of field. On the long focal length side where the depth of field is shallow, there is still a problem that image blurring occurs. This naturally requires some time before the movement of the image plane is detected by the autofocus device and the focusing lens is driven, and when this time delay is the condition on the long focus side, it is conspicuous. This is a problem that occurs because of In order to eliminate the above-mentioned time delay, it is possible to increase the speed for detecting the movement of the image plane in the autofocus device or the driving speed of the focusing lens, but the autofocus device itself is also based on the distance measuring principle. The necessary time always exists, and there is a limit to the speed increase due to the performance of the motor, the weight of the lens, and so on, and the previous time delay cannot be completely eliminated. It is also possible to reduce the amount of displacement of the image plane due to the movement of the displacement lens itself, but in this case, the lens configuration becomes extremely complicated, and the front lens fixed zoom lens as described at the beginning. Therefore, there is a new problem that there is a possibility that the characteristics of (3) will not be sufficiently obtained. The present invention has been made in consideration of the various points described above, and is an image correction capable of correcting the deviation of the image forming surface at the time of zooming operation in the front lens fixed zoom lens with a simple structure at a low cost and with almost no time delay. The purpose is to provide a device. Means for Solving Problems A zoom lens according to the present invention, in particular, an image correcting apparatus for a front fixed zoom lens, has a moving means for moving a focusing lens in an optical axis direction by a motor, and a zoom lens and a focusing lens. Lens position detecting means for detecting the current position and outputting the position information of each lens, and a focusing shown by the relationship between the zoom lens position and the in-focus lens position where the in-focus state is obtained for an arbitrary subject distance. A unit movement amount setting means for setting a unit movement amount approximate to a required movement amount of the focusing lens corresponding to a predetermined movement amount of the variable power lens in consideration of characteristics in response to an output of the lens position detection means, A correction unit that detects the current focus state and outputs correction information that corrects the unit movement amount based on the detection result, and moves the focusing lens based on the unit movement amount and the correction information. And a movement control means for outputting a movement signal to the movement means. Effect Since the image correction apparatus for a zoom lens according to the present invention is configured as described above, the movement of the focusing lens during the zooming operation is performed by the zooming lens position and the focusing lens position during the zooming operation. Based on the unit movement amount set according to the relationship, the current focus state is taken into consideration, and the movement operation is corrected by setting the unit movement amount and detecting the focus state by simple arithmetic processing. This is done by an extremely simple process of outputting information. In other words, since the correction information based on the detection of the focus state is used to set the required movement amount of the focusing lens at the time of the variable power operation, it is sufficient that the unit movement amount is set to some degree of accuracy, that is, the simple movement. It suffices to perform arithmetic processing, and therefore, during the magnification changing operation, the focusing lens quickly follows the movement of the magnification varying lens while maintaining the in-focus state. Example 1 FIG. 1 is a block diagram showing an embodiment of an image correction device for a zoom lens according to the present invention, particularly a front lens fixed zoom lens, in which 1 is a front lens fixed lens L ₁ and a variable power lens L. ₂ , a front lens fixed zoom lens composed of a focusing lens L ₃ and a vibrating lens L ₄ constituting a part of a correcting means 9 described later. Reference numeral 2 denotes a lens position detecting means for detecting the position of the variable magnification lens L ₂ and outputting the variable magnification lens position signal, and detecting the positions of the focusing lens L ₃ and the focusing lens position signal. The focusing lens position detecting means 4 for outputting 5 is a means for moving the focusing lens L _3, the focusing lens L ₃
It is composed of a motor 6 for moving the motor along the optical axis L direction and a drive circuit 7 for controlling the drive of the motor 6. Reference numeral 8 denotes a storage unit, which is provided in each of a plurality of regions obtained by dividing the focusing characteristic indicated by the relationship between the zoom lens position and the focusing lens position where a focused state is obtained for an arbitrary subject distance. The unit movement amount that is approximate to the required movement amount of the focusing lens L ₃ corresponding to the predetermined movement amount of the variable power lens L ₂ set in advance is stored, and the unit movement amount setting is performed together with the movement amount setting means 16 described later. Means 15 is constituted. Reference numeral 9 denotes a correction unit that detects the current focus state and outputs correction information for correcting the unit movement amount in the storage unit 8 based on the detection result. In the present embodiment, the correction unit is used as a focus state detection device. vibration lens L ₄ in order to utilize distance measurement principle of the known device disclosed in JP 58-188965 and JP-driving device 10 for vibrating lens L _4, the imaging device 11, the high frequency component extraction circuit 12, the high frequency component A focus state detection device comprising a focus state detection means 13 for detecting the focus states of front focus, in-focus, and rear focus by comparing the phase of the high frequency component output from the extraction circuit 12 with the vibration phase of the vibrating lens L _4. Further, it has a correction information setting means 14 for setting and outputting the correction information according to the detected focus state. Needless to say, the operation of the correction means 9 is performed independently. Reference numeral 15 is the unit movement amount setting means as described above. In this embodiment, the storage means 8 and the variable magnification lens L ₂ by the variable magnification operation are used.
Is moved by a predetermined amount, each lens position signal from the lens position detecting means 2 is received to detect one of the plurality of areas described in the storage means 8 to which the current zooming and focusing lens position belongs, and this detection is performed. A movement amount setting means 16 for taking out the unit movement amount of the focusing lens L _{3 in} the area from the storage means 8 and outputting it.
It is composed of Reference numeral 17 denotes a drive control means, which supplies a movement signal for moving the focusing lens L ₃ to the drive circuit 7 of the movement means 5 based on the unit movement amount output by the movement amount setting means and the correction information output by the correction means 9. . The operation of the embodiment of the image correction apparatus for a zoom lens according to the present invention having the above-described structure will be described below. Before that, first, the storage means 8 which constitutes the unit movement amount setting means 15 in this embodiment. The unit movement amount of the focusing lens L ₃ stored in advance corresponding to each of the plurality of areas and each of the areas, and the apparatus disclosed in JP-A-58-188965 described in the correcting means 9. The focus state detection operation will be described. FIG. 2 is a focusing characteristic diagram showing the relationship between the position of the variable magnification lens L _{2 and} the position of the focusing lens L ₃ that are in focus for a predetermined subject distance. The function shown by the curve in FIG. 2 changes variously depending on the lens configuration of the front lens fixed zoom lens, but FIG. 2 shows an example of a relatively large lens with a zoom ratio of, for example, about 6 times. . Needless to say, the vertical axis shows the focusing lens position, the horizontal axis shows the variable magnification lens position, and the right side of the drawing is the long focus side.In addition, l _{1 to} l ₅ are subject distances of ∞ and 2 m, respectively. , 1m, 0.3m,
It corresponds to 0.1m. As is clear from the characteristic diagram, in the case of the front fixed zoom lens, even if the focusing lens L ₃ is not largely moved when the variable magnification lens L ₂ is moved by the variable magnification operation, even for subjects at the same distance. Focused state cannot be obtained. Also, the amount of movement for obtaining the focus state of the focusing lens L ₃ is
It is also clear that it greatly differs depending on the position of L ₂ and the distance to the subject. Therefore, the accurate position control of the focusing lens L _{3 according} to the movement of the variable power lens L ₂ based on the characteristics of FIG. 2 causes various disadvantages as described at the beginning. Therefore, in the present invention, the characteristic shown in FIG. 2 is considered by dividing it into a plurality of regions A to G obtained by the boundary line shown by the broken line in the figure. The boundary line is set in consideration of the slope of the focusing characteristic curve shown by the solid line so that the slopes in the respective obtained regions are substantially equal, and the regions A to G based on the settings are set. Corresponds to the plurality of areas described in the storage means 8 above. By dividing as described above, the individual areas A to G
The moving characteristic of the focusing lens L ₃ required for the movement of the variable power lens L ₂ within the range is almost constant, that is, it can be regarded as a linear characteristic, and the fact that it can be regarded as a direct characteristic is an individual region. Regarding A to G, if the moving amount of the focusing lens L ₃ is set in proportion to the moving amount of the variable magnification lens L ₂ without requiring complicated calculation, the focused state is maintained and the image correction is performed. It will be considered possible. From this point, in the present invention, the predetermined movement amount ΔZ of the variable power lens L ₂ is approximated to the required movement amount ΔP of the focusing lens L ₃ required for maintaining the in-focus state, that is, the above-mentioned linear characteristic. A constant amount of movement in consideration of what can be regarded as ΔP _A ~ in each of the above areas A to G is shown in the table below.
ΔP _G is set in advance, and this multiple area A
ΔP _A ~ΔP _G set in advance in the individual ~G corresponds to a unit movement amount of the focusing lens L ₃ which is stored in the storage means 8 previously described. In addition, as is clear from the above-described embodiment, the setting of the unit movement amount is such that, in the present invention, an approximate value of the necessary movement amount of the focusing lens necessary for the movement of the zoom lens is obtained. Therefore, in addition to taking out the stored information by the area determination as described above, as shown in the partial view of FIG. 3, the object distance is obtained from the current position information of the variable magnification and focusing lens by a simple calculation. By calculating the approximate movement amount of the focal position with respect to the predetermined amount of movement of the variable power lens, that is, using the movement amount calculating means 18 for setting the unit movement amount from the above-mentioned approximate movement amount without using the previous storage means 8. It goes without saying that deployment is also possible. Next, in the present embodiment, the device adopted for detecting the focus state in the correcting means 9 will be briefly described. FIG. 4 shows a characteristic in the vicinity where the focused state of the high frequency component amount extracted by the high frequency component extraction circuit 12 is obtained from the video signal output from the image pickup device 11 when the subject distance is arbitrary and the optical path length does not change. It is the figure which showed. As is clear from FIG. 4, the amount of high-frequency components has a mountain shape with the maximum when the focusing lens L ₃ is at the focusing position Q. Incidentally, points R and S in the figure indicate the positions of the focusing lens L ₃ where the focus state is rear focus and front focus, respectively. Here, when the vibrating lens L ₄ is vibrated with the vibration waveforms A ₀ , A ₁ and A ₂ shown in FIG. 4 by the driving device 10 at each position of the focusing lens L ₃ indicated by Q, R and S, High frequency component extraction circuit 12
The output for each position of is B ₀ , B ₁ , and B ₂ , respectively. Therefore, the phases of the outputs B ₀ , B ₁ and B ₂ and the vibration waveforms A ₀ , A ₁ and A ₂
It is clear that three types of focus states of focus, rear focus, and front focus can be detected by comparing the phases of the above, and the operation such as vibration is the focus state detection operation. The focus state is detected by comparing the phases as described above.
It will be held at 13. Therefore, if the focus state is detected during the variable power operation, the movement operation based on the unit movement amounts ΔP _{A to} ΔP _G of the focusing lens L ₃ described above will match the focusing characteristics shown by the solid line in FIG. It will be possible to detect whether or not it is done. As a result, for example, when the focus state shifts to the rear focus or front focus direction and deviates from the in-focus characteristic with the selected appropriate unit movement amount, the deviation can be detected, and therefore the zooming operation is taken into consideration. Since the shift amount can be corrected, in the present embodiment, the correction amount setting means 14 sets and outputs the movement amount of the focusing lens L ₃ corresponding to the shift amount as correction information. The operation of the embodiment shown in FIG. 1 will be described below. Now, at the point X in FIG. 2, that is, the position of the variable power lens L ₂ is Z, the position of the focusing lens L ₃ is P, and the front lens fixed zoom lens 1 is located in the area E of the areas A to G. When is set, the zooming operation is performed and the zoom lens L ₂ position is set to Z.
It is assumed that the robot has moved by a predetermined movement amount ΔZ from and is positioned at Z + ΔZ. For convenience of explanation, Δ due to the movement to the long focus side
Let Z be ΔZ> O, and let the zooming operation in the opposite direction be ΔZ <O. When the displacement operation as described above is performed, the lens position detecting means 2 detects the position Z + ΔZ of the variable power lens L ₂ and the focusing lens L ₃
Position P of each unit is detected and the position information of each unit is supplied to the movement amount setting unit 16 of the unit movement amount setting unit 15. The movement amount setting means 16 detects from the position information of both lenses that the current state belongs to the area E among the plurality of areas A to G described above, and the storage means 8 corresponds to the area E. A preset unit movement amount ΔP _E of the focusing lens L ₃ is taken out, and the sign of ΔZ is determined, that is, ΔP _E is output to the drive control means 17 in consideration of the direction of displacement operation. Here, the sign of ΔZ will be briefly described. As is clear from FIG. 4, the relationship between the moving direction of the variable power lens L _{2 and} the moving direction of the focusing lens L ₃ in each of the areas A to G is opposite in some areas. Therefore, the moving direction of the focusing lens based on the unit moving amount of the focusing lens L ₃ fetched from the storage means 8 cannot be uniquely determined by the moving direction of the variable power lens L ₂ , and therefore ΔZ for each area. The focus lens L ₃
To determine the moving direction of. For convenience of explanation,
Since the movement of the focusing lens L _{3 to} the near point side is positive, and therefore ΔZ> O in the above-mentioned area E, the required movement amount ΔP of the focusing lens L ₃ is first ΔP = −ΔP _E What is done is clear from the focusing characteristic diagram of FIG. On the contrary, if ΔZ <O in the area E, the above ΔP is ΔP = Δ
Needless to say, it is P _E. The drive control means 17 supplied with −ΔP _E is a focusing lens.
A movement signal is output to the drive circuit 7 of the movement means 5 to move L ₃ to the far point side by the unit movement amount ΔP _E , and thus the focusing lens
L ₃ will be moved by the motor 6. On the other hand, the correction means 9 is also operated appropriately, and the current focus state is detected in three states of focus, rear focus, and front focus by the operation of each part described above, and the correction information according to the detection result. Δe is set by the correction information setting means 14.
In the present embodiment, the correction information Δe is the amount of movement of the focusing lens L ₃ as described above, the content of which is set to the same absolute value Δe _A , and the code thereof is in the areas A to G. It is determined in advance that “−” is set for the front focus, “+” is set for the rear focus, and Δe = O is set for the focus regardless of the position. Next, the correction information Δe is supplied to the drive control means 17 to correct the required movement amount ΔP described above. That is, when the correction means 9 is operating, if the focus state is shifted to the front focus due to the movement of the focusing lens L ₃ based on ΔP = −ΔP _E , the required movement amount ΔP of the focusing lens L ₃ is ΔP.
= -ΔP _E + Δe = -ΔP _E -Δe _A Controls to the rear pin, and if it moves to the rear pin, then controls to ΔP = -ΔP _E + Δe = -ΔP _E + Δe _A , and if in focus, ΔP = -ΔP _E The drive control means 17 outputs a movement signal for keeping + Δe = −ΔP _E as it is and moving the focusing lens L ₃ according to each ΔP. Therefore, the moving means 5 moves the focusing lens L ₃ based on the moving signal corresponding to ΔP output from the drive control means 17,
When the sign of P is positive, it is moved to the near point side, and when it is negative, it is moved to the far point side by the amount of ΔP. In the present embodiment, it goes without saying that the above-described operation is performed every time the variable power lens position detecting means 3 moves the variable power lens L ₂ by ΔZ, and as a result, the focusing lens L ₃ is moved. Will move along the focusing characteristics shown by the solid line in FIG. 2, and the image will not be blurred during the magnification changing operation, and the focused state will be maintained. It should be noted that when the zooming operation is finished and the movement of the zooming lens L _{2 by} a predetermined amount of ΔZ is stopped, the output of the zooming lens position detecting means 3 is used so that the movement of the focusing lens 4 is also stopped. Needless to say, it will be configured. Further, in the above-described embodiment, the correction information Δe by the correction means 9 is used as the movement amount and the absolute value Δe _A thereof is set as a constant value. However, for example, the correction information output from the correction amount setting means 14 is changed to the current magnification and focus. It is set in consideration of the area to which the lens position belongs, that is, the output of the lens position detecting means 2 and the output of the focus state detecting means 13 as shown in the partial view of FIG. Unit movement amount Δ
The ratio numerical value Δe ′ obtained by multiplying P _{A to} ΔP _G by the drive control means 17 can also be used as the correction information. For example, to describe the zooming operation condition in the area E described above, the required movement amount ΔP of the focusing lens L ₃ set by the drive control means 17 is set as ΔP = ΔP _E × Δe ′. In the case of focusing, unconditionally Δe ′ = 1, and since ΔZ> O in the area E, in the case of rear focus Δe ′ =
It is also possible to develop 0.9 and Δe ′ = 1.1 for the front pin. Further, when the previous correction information Δe by the correction means 9 is used as the movement amount, if the absolute value Δe _A is set to a relatively large value, it may be necessary to perform the reverse correction by the correction. Δe _A is the focus state detection means
It is needless to say that it is desirable to set the amount smaller than the detection accuracy of 13 and not causing the image blur even if the amount deviates from the focusing characteristic by the amount. It should be noted that, when the operation cycle of the focus state detection means 13 is extremely short, there is a focused state during the movement even if the movement requires reverse correction, and this focused state can be detected. Therefore, since the correction up to that point can be canceled by detecting this in-focus state, it goes without saying that it is not necessary to limit Δe _A as described above. Further, unlike the above-described embodiment, the device used for detecting the focus state in the correction means 9 is capable of outputting the focus movement amount Δe _B up to the focus of the focus lens L ₃ , for example, the focus detection device shown in FIG. Two lenses 19,2 as shown in the partial view
An arithmetic means 22 for arithmetically processing the outputs of 0, the line sensor 21, and the line sensor 21 to output the focus movement amount up to the in-focus point.
It is needless to say that the apparatus M'comprising the above can use the movement amount Δe _B as it is as the correction information Δe which is the movement amount and can expect a preferable movement operation in accordance with the focusing characteristic. Absent. Effects of the Invention In the zoom lens according to the present invention, in particular, in the image correcting apparatus for the front fixed zoom lens, the focusing lens approximates the required movement amount set based on the zoom lens position and the focus lens position during the zoom operation. Based on the unit movement amount, the focus state is taken into consideration for the movement. Therefore, the arithmetic processing required for the movement operation of the focusing lens does not require high precision during zooming operation. This is performed by a very simple calculation process of setting correction information by detection of. Therefore, if the zoom lens moves due to the zoom operation, the focusing lens starts the movement based on the set unit movement amount with almost no time delay, and the movement is corrected by the correction information. This means that there is no image blur even during zooming operation, the in-focus state is maintained, and the number of required arithmetic elements can be reduced, which has good tracking characteristics, is extremely inexpensive, and can be easily configured. doing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an image correction apparatus for a zoom lens according to the present invention, and FIG. 2 is a view showing a focused state for an arbitrary object distance of a front lens fixed zoom lens. Focusing characteristic diagram showing the relationship between the zoom lens position and the focusing lens position that are adjusted,
FIG. 4 is a partial view showing another example of the unit movement amount setting means shown in FIG. 1 in FIG. 1, and FIG. 4 is a focus state detecting means adopted in the correction means shown in FIG. FIG. 5 and FIG. 6 are characteristic diagrams of the high frequency component amount for explaining the principle of distance measurement of FIG.
Partial views showing other examples of the correction means shown in FIG. 1 ... Front fixed zoom lens, 2 ... Lens position detecting means, 3 ... Zoom lens position detecting means, 4 ... Focusing lens position detecting means, 5 ... Moving means, 6 ... Motor, 7 ... …
Drive circuit, 8 ... Storage means, 9 ... Correction means, 10 ... Drive device, 11 ... Imaging device, 12 ... High frequency component extraction circuit,
13 ... Focus state detection means, 14 ... Correction amount setting means, 15 ...
… Unit movement amount setting means, 16 …… Movement amount setting means, 17 ……
Drive control means, 18 ... movement amount calculation means, 19,20 ... lens, 21 ... line sensor, 22 calculation means.

Claims (1)

(57) [Claims] Moving means for moving the focusing lens in the direction of the optical axis by the motor, lens position detecting means for detecting magnification change and the current position of the focusing lens and outputting position information of each lens, and for any subject distance The unit position movement amount of the focusing lens corresponding to the predetermined movement amount of the variable power lens is detected in consideration of the focusing characteristic indicated by the relationship between the variable power lens position and the focusing lens position where the focused state is obtained. Unit movement amount setting means set in response to the current zooming and focusing lens position information output by the means, and correction for detecting the current focus state and correcting the unit movement amount based on the detection result. A zoom comprising a correction means for setting and outputting information, and a drive control means for outputting to the moving means a movement signal for moving the focusing lens based on the unit movement amount and the correction information. Lens image correction device. 2. The unit movement amount setting means divides the focusing characteristic indicated by the relationship between the variable magnification lens position and the focusing lens position where the focused state is obtained with respect to an arbitrary subject distance into a plurality by taking the inclination into consideration. In each of the obtained multiple areas,
A storage unit that stores one kind of unit movement amount that approximates the required movement amount of the focusing lens corresponding to a predetermined movement amount of the variable magnification lens that is set in advance; When the amount of movement is changed, one of the plurality of regions to which the current state belongs is selected by receiving the variable magnification and focusing lens position information output from the lens position detection means, and the unit amount of movement corresponding to the selected region is extracted and output. The image correction device for a zoom lens according to claim (1), which comprises a movement amount setting means. 3. The unit movement amount setting means calculates a subject distance from the magnification and focusing lens position information output from the lens position detection means, obtains a rough movement amount of the focal position by a predetermined movement of the variable magnification lens, and calculates the rough movement amount. The image correction device for a zoom lens according to claim (1), further comprising movement amount calculation means for setting a unit movement amount of the focusing lens. 4. The correction means includes a focus state detection device for detecting three types of focus states of focus, rear focus, and front focus, and zero in focus, the same absolute value in rear focus or front focus in response to the three types of focus states. The image correction device for a zoom lens according to claim 1, further comprising a correction amount setting unit that outputs, as correction information, a movement amount of the focusing lens having a different sign depending on a value. 5. The correction means includes a focus state detection device that detects three types of focus states of focus, rear focus, and front focus, and in response to the three types of focus states, at the time of focus 1, at the time of rear focus, or at the time of front focus. A correction amount that outputs as a correction information a ratio numerical value that increases or decreases the unit movement amount by being multiplied by the unit movement amount output by the unit movement amount setting means, which is set in consideration of the region to which the zooming and focusing lens positions belong. The image correction device for a zoom lens according to claim (1), further comprising setting means. 6. The correction means is a focus detection device capable of directly detecting the focus movement amount of the focus lens corresponding to the movement of the magnification lens by the magnification operation, and outputs the focus movement amount as correction information. The image correction device for a zoom lens according to the item (1).