JPH049911A - Lens position controller - Google Patents

Abstract

PURPOSE:To prevent the generation of out-of-focus in zooming by simultaneously driving a focusing motor and a zooming motor at the time of zooming, and setting up prescribed correspondence between both the motors in accordance with the result of reading of a zoom encoder. CONSTITUTION:When a zoom operation button 32 is depressed, the focusing and zooming motors 27, 29 are simultaneously driven. In such a case, a zoom position is detected by a brush 19 and a resistor base 20 and a focusing position is detected by a pulse counter as a driving variable. Both the detection signals are inputted to a CPU 33, the area including the lens, the zooming direction, and the driving direction and speed of an AF and a motor 27 are determined. When there is no difference between the reading result of the zoom encoder 23 obtained at the time of starting the motor 27 and the result of its reading obtained after the lapse of a fixed time, the driving of the focusing motor 27 is immediately stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a lens position control device for equipment such as cameras and observation equipment.

[Prior Art] Many optical design examples have been known for variable focal length photographing lenses, so-called zoom lenses, which are conventionally used in video cameras and the like. In particular, the first lens group in front of the optical axis is a lens group for focus adjustment, the second group is a lens group for zooming, and the third group is a lens group for correction.
The so-called 4 lens group performs a zoom operation by interlocking the groups in a predetermined relationship, and the fourth group becomes a fixed lens group for image formation.
Group zoom can be said to be the most common zoom lens configuration. In this 4-group zoom lens, the 1st lens group is for focus adjustment, and the 2nd and 3rd lens groups are for variable focal length.
Since they function completely separately, there is no need to move the first group in conjunction with zooming or move the second group for focus adjustment. For this reason, we were able to achieve a lens barrel mechanism with a relatively simple configuration.

On the other hand, a so-called inner focus type zoom lens is known in which the lens group for focus adjustment is a third lens group and subsequent lens groups. In the case of an inner focus type lens configuration, unlike the aforementioned 4-group zoom lens, depending on the focal length, the closest distance that can be photographed (focusing possible) when the lens group for focus adjustment is at the most extended position. changes. Especially at the wide end, it was possible to focus all the way to the front of the lens, which was a big advantage that couldn't be achieved with a four-group zoom lens. However, on the other hand, with such inner focus type zoom lenses, the lens group for focus adjustment is located behind the lens group for zooming, so even if the subject distance does not change, the focus can be adjusted by zooming. It has the characteristic that the lens group for this purpose must be moved. This had the disadvantage that the structure of the lens barrel mechanism was extremely complicated. For this reason, there have been few examples of practical use in the past. However, in recent years, with the development of automatic focus adjustment devices, a method has been put into practical use that directly evaluates the blurring of the focal plane and controls the position of the lens group for focus adjustment based on this information. By combining this type of automatic focus adjustment device with an inner focus lens, it becomes possible to position the lens group for focus adjustment at the correct position without using a complicated lens barrel structure.

4 to 7 show some examples of inner focus lenses. In the type shown in Fig. 5, the first group lens 1 is fixed, and the position of the second group lens 2 (solid line) is at the wide side focal pressure m < wide end), and at the 2' position (double-dashed line). ) is focal pressure 1 on the tele side! [(Tele end) position. Also, in this example, the third group lens 3 is linked with the second group lens in a predetermined relationship like the conventional four-group zoom, and the position 3 (solid line) is the wide end position, and the position 3 (double-dashed line) is the wide end position. is the tele end position. The lenses of the second and third groups are conventional 4
Like the lens barrel mechanism configuration of group zoom, it is linked by, for example, a cam ring. 4 is a lens group for focus adjustment, and is configured to be variable in position in the optical axis direction within a predetermined range as shown by the arrow.

In the case of Figure 's5, there is no lens group corresponding to 3 in Figure 4. Further, in this example, the lens group 4 is divided into a front lens group 4A and a rear lens group 4B, the front lens group 4A is fixed, and the rear lens group 4B is a lens group for focus adjustment and its position is variable within a predetermined range in the optical axis direction. It is composed of

In the example of FIG. 6, the first and fourth lens groups 1 and 4 are fixed, and the second lens group 2 is also at the wide end position.
The 2° position is the telephoto end position. Further, there are three lens groups for focus adjustment, and the lens group is configured to be variable in position within a predetermined range in the optical axis direction.

In the example shown in FIG. 7, the first group lens is not fixed, and the first group lens 1 and the second group lens 2 are interlocked with each other during zooming. Here, 1°2 indicates the position at the wide end, and 1' and 2" indicate the position at the telephoto end.
The lens group for focus adjustment is the rear lens group 4B at the rear end, as in the example shown in FIG.

Figures 8 and 9 show the relationship between the positions that the lens groups should take for each focus adjustment and the focal pressure of 1 m (second group lens position) for the inner focus lenses of Figures 4 to 7. 8 shows the relationship for the lens types shown in FIGS. 5 to 7, and FIG. 9 shows the relationship for the lens type shown in FIG. 4.

In the figure, the position where the vertical axis is zero is the lens group position for focus adjustment during focusing at the telephoto end.

As is clear from Fig. 8, in the case of the lens types shown in Figs. Approximately 1m
Therefore, at the telephoto end, it is about 0.6 m. Also, 'fS4
In the case of the lens type shown in the figure, for example, as shown in the figure, the distance is 0m at the wide end, and the close distance gradually becomes further away to about 1 m at the tele end.

FIG. 10 shows the basic concept of an example of an automatic focusing device that directly evaluates the blurring of the focal plane described above.

In FIG. 10(A), 17 is a screen of a video camera or the like, and 18 is a range-finding field of view which is an area from which a signal for automatic focus adjustment is extracted. 19 is a contrast pattern of the subject. FIG. 10(B) shows signal processing, and the luminance signal for the contrast pattern of a) is as shown in FIG. 10(b). If we differentiate this, we get something like (C), and if we take the absolute value, we get something like (d). The height of (e) obtained by sample-holding this is assumed to be A.

As shown in Figure 10 (C), if the horizontal axis represents the lens group position for focus adjustment and the vertical axis represents the value of A, a mountain-shaped signal is obtained.
The lens group position (B) at the peak becomes the in-focus lens position.

FIG. 11 is a block diagram showing a case where the inner focus lens shown in FIG. 5 is combined with such an automatic focus adjustment device 12, 13 as an example. 12 is a sensor, and 13 is an AF circuit that detects the in-focus state based on the output of the sensor 12. 14 is a motor which is a driving source of a driving means for making the position of the lens group 4B for focus adjustment variable in the optical axis direction.

However, in reality, with the configuration shown in FIG. 11, it is often difficult to maintain a focused state at all times, especially during zooming. This is because the automatic focusing device 12.13 detects the blur, determines whether the blur is Maevin or Atopic, and determines the rotation direction of the motor 14. This is due to the fact that the movement of only the group lens causes the lens to deviate from the miracle of maintaining focus on the specific subject distance shown in FIGS. 8 and 9.

In view of this, the same patent application filed by the Filipino applicant in 1986-10
According to No. 9966, etc., the map shown in FIGS. 8 and 9, in which the horizontal axis is the focal length and the vertical axis is the lens group position for focus adjustment, is plotted as shown in FIG. 12 (1, For example, from the differential value of the trajectory passing through the approximate center point of each block and the 8-movement speed of the second group lens 2, it is possible to calculate the focus adjustment during zooming. Determines the direction and speed at which the lens group should move, and provides a drive means for the second lens group for zooming and a drive means for the lens group for focus adjustment even if the distance measurement result of the automatic focus adjustment device cannot be obtained. It has been proposed to eliminate out-of-focus during zooming by starting driving the two driving means at the same time.

[Problems to be Solved by the Invention] The inner focus type zoom lenses shown in FIGS. 4 to 7 have the following advantages and disadvantages.

(i) The type shown in FIG. 4 has the focusing relationship shown in FIG. 9 because lens groups 2 and 3 are interlocked in a predetermined relationship during zooming.

In this case, at any one distance (■ in Figure 9)
During zooming, focus can be maintained without moving the lens group 4.

If this distance is selected appropriately, if the zoom magnification, telephoto end wide focal length, and telephoto wide zoom time are set to constant values for each type shown in Figures 4 to 7, you will be able to shoot all images during zooming. The lens type shown in FIG. 4 can often set the lens group moving speed for focus adjustment to be the slowest for possible subject distances to prevent blurring.

(ii) The lens type shown in Figure 4 has more glass pieces than other lens types, so if each design parameter is the same, the overall length will be longer than other lens types, which is disadvantageous for miniaturization. .

(iii) In the lens types shown in FIGS. 4, 5, and 6, the first lens group is fixed, and zooming and focusing can be performed correctly even when a conversion lens or the like is attached.

(iv) The lens shown in Figure 1987 can have a shorter total length at wide angle than other lens types when each design parameter is the same, and is advantageous for downsizing the lens and camera when stored.

(V) In the lens shown in Figure 7, the first group lens is movable, and if a convergence or convergence lens is attached, the load torque of the actuator will increase during zooming, and there is a risk that zooming will not be possible. be.

As mentioned above, the inner focus lens with the lens type shown in Figure 7 has sufficient value for lens miniaturization, but on the other hand, the inner focus lens has a characteristic that when a conversion lens is attached. However, this was disadvantageous in that normal zooming and focusing could not be performed.

In particular, as mentioned above, the lens group for zooming (
When moving 1 and 2) in Fig. 7 and moving the lens group 4B for focus adjustment at the same time, the "simultaneity" is defined as generating a drive command to the zooming actuator and the focus adjustment actuator at the same time. If this is achieved by doing so, there will be a problem that out-of-focus will occur at the same time as the zoom operation. That is, even if a drive command is output to both actuators at the same time, the zooming actuator cannot correctly drive lens groups 1 and 2 in FIG. 7, so only lens group 4B is driven, resulting in out-of-focus. .

This means that even if there are no accessories such as a conversion lens, if the lens barrel of the first lens group that expands and contracts can be held down by hand, the zoom button should be operated while being held down by hand. Similar out-of-focus will occur.

Therefore, while the inner focus lens consisting of the lens type shown in Figure 's7 has the advantage of reducing the size of the lens, it not only has limitations in terms of operability, but also has the serious drawback of easily causing defocus. ing.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a lens position control device capable of constructing a zoom lens that is free from the possibility of out-of-focus occurring during zooming and is advantageous for downsizing.

[Means for Solving the Problems] In order to solve the above problems, in the lens position control device of the present invention, two drive sources for driving two lens groups are started simultaneously, and while the drive sources are being driven, Two detection means detect whether or not the two lens groups are moving accurately, and the output of the detection means is monitored. If a predetermined amount of change does not occur within a predetermined time, a conversion lens, etc. It is determined that there has been an increase in the load caused by the camera user's hand or the camera user is pressing the camera down, and a control signal is issued to stop the drive source for the focus adjustment lens group.

(Embodiments) Examples of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1.2.4A and 4B are the lens groups explained in FIG. 8, and 21 is an image pickup device such as a CCD. Reference numeral 22 is an autofocus system (88) that judges based on the output of the image sensor 21 whether it is in focus or out of focus, and in the case of out of focus, what is the degree of blur, and whether the front focus is in focus or the back focus is in the case of out of focus. F) It is a device.

The distance measurement result by the AF device 22 is input to the CPU 33. 31 is a main switch, and the switch 31 is ON.
When this happens, a predetermined power-on reset is performed by the power-on reset 30.

32 is a zoom operation button, and when this button 32 is operated, the two motors 27 and 29 that are driving the zoom
The control is performed as follows. That is, the momentary zoom position is detected by the brush 19 provided integrally with the lens frame 18 of the second group lens 2 and the resistor substrate 20 in sliding contact with the brush 19, while the focusing motor 27 (in this embodiment The driving amount of the motor 27 (instantaneous movement position of the focusing lens group 4B) is measured by the focusing motor drive pulse counter 24 which counts the steps of the motor 27 (the motor 27 is a step motor).
is detected, the rain detection value is manually input to the CPU 33, and the CP
U33 uses these two position information and R in CPL133 in advance.
1 in FIG. 12, which is stored in the OM area. By comparing the area data indicated by II, . . . , it is determined to which area in the map shown in FIG. The driving direction and speed of the motor 27 are determined based on the zoom direction and the AF distance measurement results. In this way, the motor 2f and the motor 29 are driven simultaneously, and the zoom lens group and the focusing lens group are moved simultaneously.

By the way, in a conventional zoom lens, if the load on the motor 29 becomes extremely large due to the attachment of a conversion lens or the like, the motor 29 will not rotate normally, and as a result, the focusing lens group 4B will not move accurately. Therefore, there has been a phenomenon in which out-of-focus occurs during zoom driving.

In the present invention, the following control is performed to prevent the occurrence of such a phenomenon. That is, when issuing a command to simultaneously drive the two motors 27 and 29 from the CPU 33,
If there is no difference between the reading result by the zoom encoder reader 23 at the start of zoom driving and the reading result by the zoom encoder 23 after a certain period of time has elapsed, a command is immediately issued to stop driving the focusing motor 29.

FIG. 2 is a flowchart for executing the above control.

The process starts in step 101, and in step 102, it is determined whether or not a zoom operation has been performed. As a result of this determination, if a zoom operation is not being performed, the process proceeds to step 103 as a normal routine (other than when zooming). On the other hand, if it is determined that the zoom switch is being operated, the process proceeds to step 112, where the current focal length li! (or the absolute position of lens group 2) 2 is read with an encoder.

In step 104, this Z is stored in Z. In step 105, the position F of the focusing lens is also read.

In step 106, the distance measurement results from the AF device are read.

In step 107, it is read whether the zoom switch was operated in the wide direction or in the telephoto direction.

Based on the above reading results, the area is determined in step 108, the direction and speed of the focusing motor are determined in step 109, and both motors 27 and 2 are determined in step 110.
Start up 9 at the same time.

(In this case, the speed of the zoom motor 29 is a predetermined constant speed.) In step 111, it is determined whether the value of the timer T has reached a predetermined value TK. Since T=O in the first cycle, the result of step 111 is 0, and step 112
T is counted up.

In step 113, the value of Z is updated to the latest Z, and the process returns to step 105. After repeating until T=TK, T
=TK, proceed to step 114.

In step 114, the value of 2 is updated, and in step 115, this value of 2 is stored as 21.

In step 116, the timer T is cleared as T=O,
Step 117 is ΔZ = l Z l−Z ol
Perform the calculation. That is, ΔZ indicates the output difference of the zoom encoder 23 due to the time difference of TK.

In step 118, a determination is made as to whether the value is between a predetermined threshold value ΔZK and ΔZ, and if ΔZ is greater than or equal to ΔZK, it is determined that zooming is being performed correctly.

In step 119, the latest zl is stored as Zo, and the process returns to step 105.

If the determination result in step 118 is No, it is determined that the zoom motor 29 is not being driven correctly for some reason, and a command is issued to stop both motors 27 and 29 in step 120, and the zoom motor 29 is not driven correctly for some reason. In step 121, restarting of both motors is prohibited.

11 11 In the first embodiment described above, if the output difference of the zoom encoder 23 within a predetermined time is less than a predetermined value, the driving of both motors is stopped, but in this embodiment, the drive of both motors is stopped. When Δ2 is ΔZA, a ΔZ and ΔZA ratio k is calculated, and from the second cycle of the timer T, the speed of the focusing motor 27 is corrected using this k.

In this embodiment, even if the zoom speed becomes slow due to an increase in load, there is no need to stop the motor as in the first embodiment, so a lens position control device that is more practical than the first embodiment is used. Can be configured.

FIG. 3 is a flowchart for calculation. Furthermore, it is desirable that k in the first cycle after the zoom operation of the undetermined timer T be set to 1.

Third Embodiment In the second embodiment, the focusing motor 2
7 is corrected, but if k greatly exceeds 1, the zoom motor 29 may be decelerated by voltage control or the like so that k becomes 1.

This embodiment performs such control. The reason for performing this kind of control is that contrary to the aforementioned case of increased load on the zooming motor, if the zooming speed becomes too high for some reason, the required maximum speed of the focusing motor during zooming also increases. This is because when a step motor is used as in the above embodiment, there is a greater risk of step-out, so it is necessary to suppress an increase in the speed of the zoom motor as described above.

[Effects of the Invention] As explained above, the present invention relates to a lens position control device suitable for inner focus type zoom lenses in which the first group lens moves during zooming. The lens position control device according to the present invention issues drive commands to the focusing motor and the zooming motor at the same time during zooming, reads changes in the output of the zoom encoder within a predetermined time, and takes predetermined actions according to the reading results. Since the occurrence of out-of-focus inside the lens is prevented, the problems inherent in conventional lenses are solved, and the lens can be made smaller and have higher performance.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a lens position control device according to the present invention, and FIG. 2 is a flowchart of control operations executed in the device shown in FIG. 1, showing the functions of the device according to the first embodiment of the present invention. 3 are diagrams showing the functions of the device according to the second embodiment of the present invention, FIGS. 4 to 7 are diagrams showing the structure of a known inner focus lens, and FIGS. 4
Figures 10 (A) and 10 (B) are diagrams showing the relationship between the focal length and the position of the lens group for focus adjustment in the inner focus lens shown in Figures 7 to 7.
(C) is a diagram showing the basic concept of an example of an automatic focusing device that directly evaluates focal plane blur in an inner focus lens, and Figure 11 shows the inner focus lens shown in Figure 5 and Figure 10. FIG. 12 is a schematic diagram of a lens position control device configured by combining the automatic focus adjustment device shown in FIG. be. 1...First group lens 2...Second group lens (zooming lens) 4B...
Focusing lens 23...Zoom encoder 24...Focusing motor bile pulse detector 25...Focusing motor drive pulse generator 27...Focusing motor 29...Zoom motor 33... CPU 32...Zoom operation button and 4 other people (A) (B) (dl AV- (C1 Lens group position for focus adjustment)

Claims (1)

[Claims] 1. A first lens group that is moved parallel to the optical axis during zooming, and a second lens group that is moved parallel to the optical axis when the subject distance or focal length changes. and the first
A lens position control device for an inner focus zoom lens device, comprising: a zoom operation section for moving a lens group; a first detection means for detecting the position of the first lens group; a second detection means for detecting the position of the lens group; a focus detection means for detecting a focus state; a first drive source for driving the first lens group; and a second drive for driving the second lens group. and the first and second drive sources simultaneously based on the detection results by the first and second detection means and the detection result by the focus detection means when the zoom operation section is operated. A lens position control device comprising: means for detecting whether or not a predetermined change has appeared in the detection result of the first detection means after a predetermined period of time after driving.