JPH055820A - Zoom lens device - Google Patents

Abstract

PURPOSE:To obtain a zoom lens device where the intention of variable power and the intention of focusing of a photographer are introduced as a signal in an arithmetic control part, the positions of a lens group for the variable power and a lens group for correcting a focusing position and focusing are actively controlled from the arithmetic control part, out-of-focus caused by the quick change of a detected value is prevented, a driving part is miniaturized, and high reliability and low cost are accomplished. CONSTITUTION:This zoom lens is provided with a variable power lens group 2, a lens group 4 for correcting the out-of-focus and focusing, and a means for driving and positioning the respective lens groups, and an arithmetic control part 24 for controlling the respective driving means is provided with a memory 25 which incorporates the position table of each lens group and where the position of each lens group is stored, and the position of the lens is controlled by comparing the position table with the memory according to the signal of instructing means 20-22 for instructing the variable power, etc., to the arithmetic control means 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens device, and more particularly to a zoom lens device which actively controls a lens position for zooming and focusing.

[0002]

2. Description of the Related Art In recent years, in zoom lenses, instead of controlling the lens position by a cam or the like, a control method of setting the position of the lens group by performing calculation based on the detection value from the position detecting means of each lens is used. Therefore, there are no restrictions such as defects due to the shape of the cam groove. For example, Japanese Patent Publication No. 52-15226 discloses a first detecting means for detecting a focal length setting value of a variable power lens system and a second detecting means for detecting an image forming setting position. And a zoom focus method for determining the position of the lens group by calculation based on the detection values of the first and second detection means, and controlling the lens group position accordingly to keep the imaging position constant. ing.

[0003]

However, such a conventional example has the following problems when the detected value changes with time. When the detected value changes faster than the response speed of the lens group position setting means, it becomes difficult to keep the image forming position constant. The position setting means capable of following the expected change in the detected value at a high speed becomes large and expensive, and it is difficult to mount the position setting means particularly on a camera for amateur use.

The present invention uses a passive control method of detecting the positions of the lens group for zooming and the lens group for focus position correction and focusing, and performing arithmetic control, to change the user's intention of zooming. A signal is introduced to the arithmetic control unit via each instruction means such as focus adjustment intention, and the arithmetic control unit actively controls and sets the lens group position for zooming and the lens group position for focus position correction and focusing. by doing,
It can be controlled by the optimum control speed according to the drive capacity of the drive unit, prevents defocus due to change in detection value above the above capacity, prevents the drive unit from becoming large-scale and expensive, and is compact and highly reliable. The purpose is to obtain a low-priced zoom lens device.

[0005]

[Means for Solving the Problems] That is, a lens group that moves for zooming, a lens group that moves for focal point correction and focusing due to zooming, and a means for driving and positioning each lens group. In the zoom lens having, the arithmetic control means for controlling each drive means has a built-in position table of each lens group, and has a memory for storing the position of each lens group. The image forming position is made constant by comparing the position table with the memory and controlling the lens position according to the signal from the magnification instruction means.

The above zoom lens apparatus also includes focus state detection means for driving and controlling the focusing lens group to obtain the best focus state, and further includes focus adjustment instruction means and automatic focusing or electric focus adjustment. When the electric focus adjustment is selected, the automatic focusing control is stopped, and the focusing lens group can be drive-controlled based on the signal from the focus adjustment instructing means.

Furthermore, since a cylindrical cam barrel is not required, the lens shape can be made smaller and lighter, the lens barrel structure can be simplified, and a stepping drive means such as a stepping motor can be used. Thus, it is possible to provide an apparatus which can be driven more smoothly without applying an extra load to each lens group and can be configured at low cost by controlling the position detection means of each lens group.

[0008]

EXAMPLES The present invention will be described in detail below based on examples. FIG. 1 shows a block diagram of one embodiment. In the figure, 1 to 4 show an example of a zoom lens system, 1 is a fixed lens group, 2 is a lens group for zooming, 3 is a fixed lens group, 4 is a focusing lens group, but a focusing lens group Four
In order to correct the focus shift that occurs with the movement of the lens group 2 for zooming, the zoom lens is driven simultaneously while maintaining a certain relationship during zooming. Further, even with a zoom lens having a five-group structure in which a fixed lens group is arranged behind the focusing lens group 4, the structures of the following embodiments can be applied as they are.

Lens movements for zooming and focusing are controlled by the arithmetic control unit 24, and focusing is performed by rotating the screw shaft 13 by the drive motor 15 via the drive circuit 16 and engaging the lens group 4 therewith. The holding frame 14 is moved. Further, for zooming, the screw shaft 8 of the drive motor 9 is driven via the drive circuit 17 to move the holding frame 7 of the lens group 2, and at the same time, the above-mentioned drive circuit is arranged so as to correct the defocus that occurs during zooming. The lens group 4 is moved simultaneously via 16. The drive amount is determined based on the position table stored in the memory 25 in the arithmetic control unit 24. One example is shown in FIG.
In the table of FIG. 7, X (i) corresponds to the position of the second lens group, and Y (i, j) corresponds to the position of the fourth lens group.
Each curve in the figure shows the lens group position at the time of zooming with respect to a certain object distance, and if the object distance changes, it moves to a different curve of j corresponding to the upper and lower object distances. In the figure, [X (i), Y (i, ₀ )] is [X
(i, Y (i, N)] is the zoom curve of the closest object distance,
[(X (i), Y (i, M)] indicated by a dotted line is a group of curves at the macro position.

Further, in the figure, 5 and 6 are low-pass filters and image pickup devices, 18 is a signal processing circuit thereof, and 19 is a focus signal detection circuit. Photo interrupters 11 and 23 are used for initial positioning of the lens group by the light shielding plates 10 and 26 provided on the lens holding frames 7 and 14. Numerals 20 to 22 are manual switches, 20 is a magnification change direction instruction switch, 21 is an auto / manual selection switch, and 22 is a focus adjustment direction instruction switch.

In this system, when the power is turned on, the arithmetic and control unit 24 in which the program flow of FIG. 3 is stored executes an initialization routine, and the variable power lens group 2, the lens group 4 for focus position correction and focusing. Are driven in the direction of the photo interrupters 11 and 23, which are the initial setting positions, and when the outputs of the photo interrupters 11 and 23 reach a predetermined signal level, the position memories MX and MY of the lens group 2 and the lens group 4 are set. Reset to a predetermined value (eg 0). At the same time, the AF control mode flag FM and the focusing lens control direction designation flag FD are also initialized. Next, according to the selected state of the automatic / manual selection switch 21, the processing of each of the following modes is executed.

1. When the switch 21 is for manual M selection FIG. 4 shows a processing flow in this case. The arithmetic control unit 24 is in a state of waiting for signals of the magnification change instruction switch 20 and the focus adjustment instruction switch 22. When the switch 20 outputs a signal indicating the direction of the telephoto side T or the wide angle side W, the position memory MX,
According to [X (i), Y (i, j)] stored in MY, [X (i), Y is stored in the position table 25 of the lens group 2 and the lens group 4 stored in the arithmetic control unit 24. (i, j)] is selected, and if the switch 20 is on the telephoto side, the content of the memory MX is set to X (i-1), and the corresponding Y (i-1, j) is placed in the memory MY. The lens groups 2 and 4 are driven in the optical axis direction by corresponding amounts by the stepping motors 9 and 15, respectively. As described above, the predetermined position table 25
Since the lens group is driven according to the inside curve [X (i), Y (i, j)], the focal position remains constant. Switch 2
By repeating the above procedure while 0 is being pressed,
Zooming is performed while keeping the focus position constant. or,
When the switch 22 is pressed, MY is updated while MX is constant at X (i). When the switch 22 is pushed to the near side N, the memory MY is added, the content is changed to Y (i, j + 1), the lens group 4 is extended accordingly, and when pushed to the far side F, MY is subtracted. , The lens group 4 is retracted accordingly, but the reference curve [X (i), Y (i,
If it is controlled up to ₀ )], it will not be subtracted even if it is pressed further. The close-up side is arbitrary because it is determined by the design of each lens system, but in this embodiment, the focusing operation is j (N) corresponding to the closest focusing distance Y (i, j).
= (Yi, N) and beyond that, even if the switch 22 is pressed, the lens group 4 is stopped and the input is ignored. (M
X, MY) is the normal shooting distance range [(X (i), Y (i, ₀ )] ~
When riding on one of the curves within the range of [X (i), Y (i, N)], the focus position remains constant for each object distance j even when zooming from the telephoto end to the wide-angle end. However, in the macro region curve group [X (i), Y (i, M)], Y (i, M) = (Yi, N) holds.
The focus position can be maintained only from (i) to the wide-angle end.

The numerical values of the curve group are actually stored as digital values, and the digital position closest to the curve in FIG. 7 is [X (i), Y
(i, j)] table is stored and read out, and a slight position error due to digitization occurs between the analog amount and the digital amount. However, this error is within the depth of focus. The step step of movement and the step step of the zoom side are determined.

2. When the switch 21 is in the automatic A selection mode The process flow in this case is shown in FIG. In this system, priority is given to magnification change, and when the magnification change instruction switch 20 is pressed, automatic focusing control is stopped. Zoom control of MY and M
It is performed by the value of X, and zooming is performed while maintaining the focus position.

When the scaling signal is not output and the AF control mode flag FM is in the swing mode for detecting the focusing direction, that is, FM = I, the arithmetic control section 24 causes the video signal processing section 18 to operate. While monitoring the strength of the focus signal input through the focus signal detection unit 19, the lens group 4 is moved to the strength of the focus signal and the BP in the focus signal detection unit 19.
An appropriate swing amount α is set according to the selected state of the filter 19-2-i, and the swing for detecting the focus direction is performed. For example, as shown in FIG. 8, the focus signal P (i) at the Y (i, j) position is set to Y (i, j + 1) by moving the lens group 4 to the near side N by a fixed amount α. If P (i + 1) ≧ P (i) + Δ as compared with the signal P (i + 1), it is expected that a significant increase of the focus signal is expected if the lens group 4 is further driven to the near side. Then, the focusing lens control direction designation flag FD is set to drive the focusing lens group 4 in the closest direction (FD ← N), and the AF control mode flag FM is set to mode II for finding the peak of the focus signal ( FM
← II), and the lens group 4 is driven in the direction of the shortest distance until the peak is reached. Here, Δ is an amount selected according to the focus signal P (i) currently obtained, the spatial frequency band of the bandpass filter being used (lens aperture diameter, subject brightness information), and the like. On the contrary, if P (i + 1) ≦ P (i) + Δ, further driving of the lens group 4 to the near side is expected to significantly reduce the focus signal, and the focusing lens control direction designation flag FD Is set to drive the focusing lens group 4 toward the ∞ side (FD ← F), and the AF control mode flag FM is set to mode II (FM ← II) for finding the peak of the focus signal, and the peak is reached. The lens group 4 is driven in the ∞ direction.

Even if P (i + 1) ≧ P (i) + Δ, P (i + 1) ≦ P (i) +
If not Δ, the focus signal has reached a peak, that is, it is determined that the focus is achieved, and the focusing lens is stopped (F
D ← I) is done. In addition to the above, in order to determine the peak, the previous focus signal P (i) and the next signal P (i + 1) are compared, and the maximum values Pmax and P (i +) of the focus signal up to several steps before are compared.
When comparing 1), the former decreases by Δ or more, and P (i + 1) <Pm
If it is ax, there is also a method of judging that the focusing lens group position where Pmax was present is the peak and returning to that position.

When the AF control mode flag FM is set to the mode II, the focus lens group 4 is driven while monitoring the focus signal to the infinity side or the close range side depending on whether the focusing lens control direction designation flag FD is F or N. However, if no significant change is observed even if a small amount of α is driven, that is, | P (j ± 1) -P (j) | <
When Δ, it is determined that the peak of the mountain in FIG. 8, that is, the in-focus state, or the contrast of P (j ± 1) ≈P (j) ≈0 is extremely low, and the focusing lens is used. It is judged that it is not the situation to move the lens, the lens driving is stopped, and the focus direction detection is further continued. Therefore, FD = I is set, and FM is not updated, and the process proceeds to the next step. Where Δ
Is used for the determination of low contrast as well as the determination of focus and non-focus. To determine the contrast, another value Δc is used to compare with the current focus signal P (i), and P
If (i) <Δc, there is also a method of keeping the focus direction detection without moving the focusing lens as a low contrast.
The low contrast discrimination value Δc can be dynamically changed depending on the diaphragm system and zoom position of the lens and the focus detection area to realize more appropriate automatic focusing control.

In FIG. 2, 19-1 is a timing circuit, and 19
2-1 to 19-2-N are filters for extracting a signal in a specific frequency band from a video signal, 19-4 is a rectifier circuit, 1
Reference numeral 9-5 is an integrating circuit, and 19-6 is an interface circuit for sending a focus signal to the arithmetic control unit.

Another feature of this system is that the arithmetic control unit stores the table information [X (i), Y (i, j)] corresponding to the object distance U and the focal length f. It is possible to display such useful information and preset the lens state. Display of subject distance and focal length The display calculation control unit has a group of [X (i), Y (i, j)] curves,
Since X (i) is the focal length of the zoom and j is a number having a 1: 1 correspondence with the subject distance, these can be used to know the focal length and subject distance in detail. For example, a display element using liquid crystal or the like may be configured on the lens frame of the lens, and a signal may be sent from the arithmetic control unit to display the selected focal length or subject distance. Preset of focal length, subject distance, and magnification A desired focal length and subject distance can be set by specifying X (i) and j by a numerical signal to the arithmetic control unit from an input device (not shown) from the camera side. In addition, the zooming range can be arbitrarily designated, and the zoom range can be limited depending on the user's shooting technique level and shooting intention. Further, it is possible to easily focus automatically while selecting the focal length and the subject distance so that the photographing magnification becomes constant. For example, when a bust shot or a specific magnification value is sent from the camera side to the calculation control unit, the zoom and focus are controlled to have desired magnifications. This function is most suitable not only for shooting outdoors but also for applications where it is desired to capture a document or a still life on the screen at a fixed ratio (for example, as an image for printed matter).

As a modification of the above-described embodiment, the zoom switch and the focus switch are not simple seesaw switches but dials or rings with incremental encoders whose rotation direction can be recognized, and the output from the operation is input to the arithmetic control section. It is possible to realize a zoom lens device having a better operation feeling. As another modification, instead of a zoom switch or a focus switch, a rotary ring using encoders that respectively indicate the absolute value of the rotation angle is used, and by displaying the focal length and subject distance on the ring, conventional front focus, It is possible to provide a zoom lens device having an operation feeling and appearance similar to those of a mechanical zoom type lens.

Further, it is also possible to use other driving means such as a piezo actuator, particularly a scale insect structure, as the driving means for the variable power lens group 2 and the focusing lens group 4 instead of the stepping motor.

As still another modification, the driving means D for generating an incremental pulse with the movement of the lens group
C motor, memory MX, M depending on the generated pulse
It is also possible to rewrite Y and control while comparing with the [X (i), Y (i, j)] table.

Further, a positioning device such as a photo interrupter used for initializing each lens group is abolished, a stopper is provided, and each lens group is once abutted against the stopper to mechanically initialize the lens group position. It is also possible to control. Furthermore, as a focus state detection device, a device that detects a subject distance without using a video signal, for example, an infrared active type trigonometric rangefinder using a light emitting element or a light receiving element or a pair of passive sensor arrays is used. A pair of images formed by a pair of lenses separated from each other by a predetermined baseline length is formed on each sensor, and an output from a device that detects the distance from the relative positional relationship detects an in-focus state from an automatic focusing device. It may be controlled by a signal.

[0024]

As described above, according to the present invention, the position detecting means for each lens group as in the conventional example is not provided.
Moreover, since the variable magnification lens group and the focusing lens group are actively positioned from the arithmetic control unit, high speed,
A highly accurate and inexpensive zoom lens device can be achieved.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of a zoom lens device according to the present invention.

FIG. 2 is a block diagram of a focus signal detection circuit according to the above embodiment.

FIG. 3 is a flowchart showing an outline of control in the above embodiment.

[Fig. 4] Flow chart for manual control

FIG. 5 is a flowchart for automatic control.

FIG. 6 is a flowchart of a focus control mode.

[Figure 7] Focus curve group

FIG. 8 is a video signal diagram for focus detection.

[Description of Reference Signs] 1 fixed lens group 2 variable power lens group 3 fixed lens group 4 focusing lens group 5 low-pass filter 6 image sensor 7 screw shaft 8 of drive motor 9 holding frame for lens group 2 having a female screw to engage 10 , 26 light-shielding plate 11, 23 photo interrupter 12 for initial positioning 12 auto iris 14 screw shaft 13 of drive motor 15 holding frame of lens group 4 having female screw 14 to be engaged 16, 17 drive circuit for drive motors 9 and 15 respectively Signal processing circuit 19 Focus signal detection circuit 20 Magnification change direction instruction switch 21 Auto manual instruction switch 22 Focus adjustment direction instruction switch 24 Arithmetic control unit 25 Zoom focus curve position table 19-1 Timing circuit 19-2-1 to 19-2- N Video signal to specific frequency Filter for extracting signals in several bands 19-4 Rectifier circuit 19-5 Integration circuit 19-6 Interface circuit for sending focus signal to operation control unit

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 13, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 7]

[Figure 4]

[Figure 5]

[Figure 6]

[Figure 8]

Claims (1)

Claim: What is claimed is: 1. A lens group that moves for zooming, a lens group that moves for focal point correction and focusing due to zooming, and means for driving and positioning each lens group. In the zoom lens having, the arithmetic control means for controlling each driving means has a built-in position table of each lens group, and has a memory for storing each lens group position,
A zoom lens device characterized in that the image forming position is made constant by comparing and controlling the position table and the memory by a signal from the magnification changing instruction means for instructing the arithmetic control means to change the magnification. Item 1. A zoom lens device including a focus state detection unit, which drives and controls a focusing lens group to achieve the best focus state. 3. A focus adjustment instruction unit and an automatic lens system according to Claim 2. A switch means for selecting focusing or electric focus adjustment is included, and when electric focus adjustment is selected, automatic focus control is stopped and drive control of the focusing lens group is performed based on a signal from the focus adjustment instruction means. 4. A zoom lens device according to claim 1, wherein the drive means is a stepwise drive means.