JPH0943483A - Lens controller and lens position adjusting method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens position controller capable of eliminating the amount of blur in the middle of zooming and also capable of eliminating the error of focal distance without tightening up the accuracy of manufacture, that is, allowable error. SOLUTION: A memory storing the focusing position of a focusing lens 105 with respect to a variable power lens position in accordance with an object distance is provided for adjusting a lens system provided with the variable power lens 102 and a focusing lens 105 for correcting the movement of a focusing surface in the case the lens 102 moves; the telephotographic end of a variable power lens group and the reference position of a focus lens group are set based on the information of the positions of the lens 102 on a wide side, on a telephotographic side and on an intermediate point and the information of the focusing positions of the lens 105 on the respective set positions of the lens 102, so that the wide end is set as the reference of the telephotographic end, and the focusing position on the wide end is stored as the wide end reference position of the lens 105.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens control device suitable for use in an inner focus type lens system.

[0002]

2. Description of the Related Art FIG. 2 shows a simple structure of an inner focus type lens system.

In FIG. 2, 101 is a fixed first lens group, 102 is a second lens group for varying magnification (hereinafter referred to as variable magnification lens), 103 is a diaphragm, and 104 is a fixed first lens group. The third lens group 105 is a fourth lens group (hereinafter referred to as a focus lens) 105 having a focus adjustment function and a so-called competition function for correcting the movement of the focal plane due to zooming, 106 is an image sensor, and 106a is It is an imaging surface.

As is well known, in the inner focus type lens system configured as shown in FIG. 2, since the focus lens 105 has both a compensator function and a focus adjustment function, even if the focal lengths are the same, the image pickup surface 1 is not affected.
The position of the focus lens 105 for focusing on 06a varies depending on the subject distance.

Even if the subject distances are the same, if the focal length changes due to the zooming operation, the focus lens position for focusing becomes different.

When the position of the focus lens 105 for focusing on the image pickup surface is continuously plotted while the variable power lens is being driven to perform the variable power operation for each object distance, FIG. become that way.

In FIG. 3, the abscissa axis represents the zoom lens position, that is, the focal length, and the ordinate axis represents the focus lens position, that is, the subject distance.

During the zooming operation, if one of the loci shown in FIG. 3 is selected according to the object distance and the focus lens 105 is moved according to the locus,
This allows variable magnification operation without blur.

Incidentally, in the front lens focus type lens system, an independent compensator lens is provided for the variable power lens, and the variable power lens and the compensator lens are connected by a mechanical cam ring.

Therefore, for example, when a knob for manual zoom is provided on this cam ring and the focal length is manually changed, no matter how fast the knob is moved, the cam ring will follow this and rotate to change the magnification. Since the lens and the competing lens move along the cam groove of the cam ring, if the focus lens is in focus, the above operation does not cause blurring.

However, in the control of the inner focus type lens system having the above-mentioned features, the plurality of locus information shown in FIG. 3 is stored in the lens control microcomputer in some form and changed from the focus lens. In general, a locus is selected and specified according to the position of the double lens, and zooming is performed while tracing the selected locus.

Further, since the position of the focus lens with respect to the position of the variable power lens is read from the memory in the microcomputer for lens control and is applied for lens control, the position of each lens is not read with a certain degree of accuracy. must not.

As is clear from FIG. 3, in particular, when the variable power lens moves at a constant speed or a speed close to it, the inclination of the locus of the focus lens changes every moment due to the change of the focal length.

This indicates that the moving speed and the moving direction of the focus lens change every moment, in other words, the actuator of the focus lens must make an accurate speed response from 1 Hz to several hundreds Hz. It will not happen.

As an actuator that satisfies the above requirements, it is becoming common to use a stepping motor for the focus lens group of the inner focus lens system.

The stepping motor rotates in perfect synchronization with the stepping pulse output from the lens controlling microcomputer and the stepping angle per pulse is constant, so that the stepping motor has high speed response, stopping accuracy, and position. It is possible to obtain accuracy.

Further, when a stepping motor is used,
Since the rotation angle with respect to the number of step pulses is constant, the step pulse can be used as it is as an increment type encoder, and there is an advantage that no special position encoder needs to be added.

As described above, when the zooming operation is performed while keeping the focus by using the stepping motor, the locus information of FIG. It is also necessary to read the locus information according to the position or moving speed of the variable power lens and move the focus lens based on the information.

However, in the actual lens system, the locus information stored in accordance with the optical design value, that is, the zoom tracking data is created as described above, whereas in reality, each lens group has This locus does not conform to the design value due to the focal length error. For this reason, in an actual video camera, among the stored data, the work for adjusting the telephoto end and the wide end to correspond to the position of the zoom lens is performed.

As this method, conventionally, the stroke of the variable power lens from the tele end to the wide end is kept as designed, and the focusing position difference (balance) between the tele end and the wide end at the adjustment distance (for example, ∞). ) Is also calculated to be a design value, and there is known a method of setting it at the tele end and the wide end. This adjustment method will be referred to as constant stroke adjustment here.

Further, the difference (balance) between the focus positions of the focus lenses at the tele end and the wide end is set as a design value, and the position at which the focus lens goes up most on the map at the middle (intermediate focal length) and the tele position. A method is known in which a zoom lens position is obtained such that the amount of movement from the focus lens position at the end becomes a design value and the positions of the zoom lens at the tele end and the wide end are set. This adjustment method is referred to as tele-middle tracking adjustment here.

Next, referring to FIG. 4, when the constant stroke adjustment and the tele-middle tracking adjustment are performed, the tele end position and the wide end position are set so that the position of the focus lens in the middle becomes larger than the design value. The situation when the lens group having an error is used will be described.

In FIG. 4, the horizontal axis shows the position of the variator lens (that is, the focal length), and the vertical axis shows the position of the focus lens. In the figure, the trajectory Sb indicated by the solid line corresponds to the design value. On the other hand, it is assumed that the actual focus lens shows a locus Sa like a dotted line.

At this distance (for example, ∞), the difference between the in-focus positions of the focus lens at the tele end T and the wide end W is zero.

Assuming that the trajectory is as designed, a point on the map is the starting point of the adjustment when the tele-middle tracking adjustment is performed. From this point, the focus lens is lowered downward in the figure by the designed amount of movement A of the focus lens. This position becomes. From this state, the zoom lens is moved to obtain the in-focus position, and this is set as the zoom lens position at the telephoto end.

Further, in this example, since the difference between the focus lens focus positions at the wide end and the tele end is 0 as described above,
Similarly, the position where the variable power lens is moved and focused is the variable power lens position at the wide end.

In the case of the constant stroke adjustment, the stroke and the balance are adjusted to a predetermined position regardless of whether the trajectory is the designed value or the trajectory having a certain error indicated by the dotted line. Also, the tele end position becomes, and the wide end position becomes.

On the other hand, with a lens having a dotted line trajectory Sa,
In the case of performing the middle tracking adjustment, when the focus lens is moved downward in the figure by the design value A from the adjustment start point ', the position becomes the position'. From here as well as the above, as a result of moving the variator lens to the in-focus position,
Is the tele end T'and the wide end W '.

As described above, when there is an error such that the height of the "mountain" of the locus rises with respect to the design value (solid line) as shown in FIG. 4 (dotted line), if the constant stroke adjustment is performed, the tele end is obtained. Is the wide end, and the tele end is the wide end when the tele-middle tracking adjustment is performed.

Accordingly, the tele-middle tracking adjustment has a smaller intermediate blur than the constant stroke adjustment,
The focal length varies.

[0031]

As described above, in the conventional apparatus, by controlling manufacturing error or the like, the variation in focal length that occurs or the amount of blurring that occurs during zooming is suppressed to a level that does not cause a problem. However, the zoom ratio of the zoom lens mounted on the video camera lens has tended to increase in recent years, and the standard zoom ratio of several years ago was about 8 times, while it is already 12 times or 18 times. High-magnification zooms such as these have been commercialized, and there is a great need for higher magnifications going forward.

With such a high-magnification zoom, the locus is likely to be affected by the positional accuracy of each lens group, the variation of the focal length, and the like.

Further, the size of the image pickup device (CCD) has been changed from 1/3 inch to 1/4 inch in the diagonal dimension, and there is a great need for miniaturization in the future.
If the power of each lens unit is increased for downsizing, there is a concern that the error locus is likely to be affected.

Under such a background, it is becoming difficult to keep the above-mentioned focal length error and the amount of blurring occurring in the middle of zooming within the target values by conventional manufacturing error management.

Therefore, an object of the present invention is to provide a lens position control device which eliminates the above-mentioned blur amount in the middle of the zoom and also eliminates the error in the focal length without increasing the manufacturing precision, that is, the tolerance. Especially.

[0036]

In order to solve the above-mentioned problems, according to the invention described in claim 1 of the present application, a first lens group for performing a magnification change operation, and the first lens A second lens group for correcting the movement of the focal plane when the group moves; a driving means for independently moving the first and second lens groups parallel to the optical axis; A detection unit that independently detects the second lens group position, a storage unit that stores the focus position of the second lens group with respect to the first lens group position according to the subject distance, and a predetermined subject distance. , The wide side, the tele side, and the position of the first lens group at the intermediate point, and the information of the in-focus position of the second lens group at each setting position of the first lens group, the first lens group Set the tele end of and the reference position of the second lens group. , The telephoto end is set to the wide end as a reference, the focus position in the wide-angle end and the second
And a control unit that stores the wide end reference position of the lens group.

According to a second aspect of the present invention, in the first aspect, the control means is the first
From the information in which the focus position of the second lens group with respect to the position of the second lens group is stored according to the subject distance, the wide end position of the first lens group, and the wide end reference position of the second lens group. , The focus position on the wide side according to the subject distance is calculated.

According to the invention of claim 3 in the present application, the first lens group for performing the zooming operation, and the first lens group for correcting the movement of the focal plane when the first lens group is moved. A lens position adjusting method of a lens control device comprising two lens groups, wherein three positions of the first lens group at least at a wide side, a tele side and an intermediate point are set at a predetermined object distance, The focus positions of the second lens group at the three setting positions of the first lens group are respectively detected, and the set positions of the first lens group and the focus positions of the second lens group are detected. From the information of
A telephoto end of the first lens group and a reference position of the second lens group are set, a wide end is set with the telephoto end as a reference, and a focusing position of the second lens group at the wide end is set. A lens position adjusting method for setting the wide end reference position of the second lens group is used.

Further, according to the invention of claim 4 in the present application, in the information of claim 3, the focus position of the second lens group with respect to the position of the first lens group is further stored according to the object distance. Then, the focus position on the wide side according to the object distance is calculated from the wide end position of the first lens group and the wide end reference position of the second lens group.

[0040]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 shows a first camera of the present invention.
3 is a block diagram showing the configuration of the embodiment of FIG.

In the figure, 101, 102, 103,
Reference numerals 104 and 105 respectively denote elements that constitute an inner focus type lens system, and include a fixed front lens group, a second lens group (magnifying lens) for performing zooming, an aperture stop, and a fixed third lens group. It is a lens group and a fourth lens group (referred to as a focus lens) having both a competition function and a focusing function. Elements corresponding to those in FIG. 2 are designated by the same reference numerals.

The image light transmitted through this lens system is imaged on the image pickup surface 106a of the image pickup element 106, photoelectrically converted into an image pickup signal and outputted.

Reference numeral 107 denotes an amplifier or impedance converter, and reference numeral 108 denotes a camera signal processing circuit for performing a predetermined signal processing on the image pickup signal output from the amplifier 107 to convert it into a standardized video signal. The generated video signal is amplified to a specified level by an amplifier 109, and an LCD (liquid crystal display) as an electronic viewfinder.
After being processed by the display circuit 110, the captured image is displayed on the LCD 111.

On the other hand, the image pickup signal amplified by the amplifier 107 is sent to the aperture control circuit 112 and the AF evaluation value processing circuit 115.

In the aperture control circuit 112, the IG driver 113 and the IG meter 114 are selected according to the video signal input level.
Is driven to control the aperture amount of the diaphragm 103 to adjust the light amount.

In the AF evaluation value processing circuit 115, in response to the gate signal from the distance measurement frame generation circuit 117, only the video signal corresponding to the distance measurement frame is extracted from the image pickup screen, and the focus state is also detected. The focus detection operation is performed by extracting only the high-frequency component that changes.

Reference numeral 116 denotes an AF processing microcomputer (hereinafter referred to as an AF microcomputer), which performs drive control of various lenses and ranging frame control for changing the ranging area according to the AF evaluation signal strength. There is. The AF microcomputer corresponds to the calculating means of the present invention. The storage means of the present invention is also constituted by a ROM provided in the AF microcomputer, and stores the representative cam loci as shown in FIGS. 3 and 4.

Further, the AF microcomputer 116 is in data communication with a system control microcomputer (hereinafter referred to as "syscon") 122 which controls the entire apparatus, and the syscon 122 includes a zoom switch (SW) 12
Operation information of 3 (a unitized zoom SW outputs a voltage according to the rotation angle of the operation member, and variable speed zoom is performed according to this output voltage) is read by A / D conversion or the like. The zooming information controlled by the AF microcomputer 116 during zooming, focal length, and other zooming operation information are exchanged with each other.

Reference numerals 118 and 120 denote AF microcomputer 1 respectively.
A zoom driver, a focus driver 119, and a zoom driver 119 for outputting drive energy to a lens driving motor in accordance with drive commands for the variable-magnification lens 102 and the focus lens 105 output from the zoom lens 1, respectively.
02 and a focus motor for driving the focus lens 105.

Hereinafter, assuming that the lens driving motor is a stepping motor, a method of driving the motor will be described.

The AF microcomputer 116 determines the drive speeds of the zoom motor 119 and the focus motor 121 by a program process, and uses them as a rotation frequency signal of each stepping motor to drive the zoom motor 119.
8. Send to the driver 120 for driving the focus motor 121.

The drive / stop commands for the zoom motor 119 and the focus motor 121 and the rotational direction commands for the respective motors are also issued to the zoom driver 118 and the focus driver 120.
I am sending it to.

The drive / stop signal and the rotation direction signal are mainly used for the zoom motor 119.
Depending on the state of the unit 123, the focus motor 12
Regarding No. 1, the drive command is determined by the processing in the AF microcomputer 116 during the AF operation and the zoom operation.

Each driver responds to the rotation direction signal by 4
By setting the phases of the motor excitation phases of the two phases to forward rotation and reverse rotation, and changing the applied voltage (or current) of the four motor excitation phases according to the received rotation frequency signal, and outputting. The output to each motor is turned on / off in response to the drive / stop command while controlling the rotation direction and rotation frequency of the motor.

Further, since the stepping motor is used and the rotation angle with respect to the step pulse number is constant, the step pulse is used as it is as an increment encoder to detect the zoom and focus positions.

FIG. 5 is a flowchart showing the processing operation in the AF microcomputer 116 when the focus adjustment, which is a feature of the present invention, is performed.

The process starts at step 501. step5
In 02, the position of the variable power lens 102 on the optical axis is set to a zoom position (position in FIG. 4 ′) corresponding to the vicinity of the peak of the mountain where the locus of the focus lens 105 becomes a mountain.

Next, in step 503, the focus motor is set to 12
1 is driven to move the focus lens 105 to perform focusing. Note that the subject distance is set to the adjustment distance here, and the subject such as a chart for some adjustment is arranged.

In step 504, it is checked whether or not there is focus, and the focus lens 105 is moved until it comes into focus.

Actually, by the AF operation of the video camera, by checking the correlation between the focus voltage signal output from the AF evaluation value processing circuit 115, which is related to the contrast of the object, and the moving direction of the focus lens 105, the focusing movement is achieved. Although the focus position is searched while deciding the direction, the details of the AF operation algorithm itself are omitted for simplicity.

When it is confirmed in step 504 that the focus has been achieved, the focus lens is lowered by A based on the design value in step 505 (the expression of lowering is referred to in FIG. It shows that you will go, in fact, depending on the zoom type of the zoom lens,
Sometimes it extends to the subject side, and sometimes it extends to the image plane side).

At step 506, the variable power lens 102 is driven from this state toward the telephoto side T. Also at the same time step5
At 07, it is determined whether or not the subject is in focus.

When the movement of the zoom lens 102 is completed and the focus is achieved at that position, the zoom lens position at that time corresponds to the zoom lens position at the telephoto end.

Then, in step 508, the position of the zoom encoder in that state (count value of the stepping pulse number of the stepping motor) is used as a value for defining the position of the tele end, and is stored in the ROM in the AF microcomputer 116 or the external E ² PROM.
The data is stored in the writable and non-volatile memory Vt '.

In step 509, the focus lens is moved in the optical axis direction by the balance corresponding to the difference between the focus positions of the focus lens in the adjustment distance between the tele end and the wide end. However, when the balance is 0 as shown in FIG. 4, it is not necessary to move.

Similarly to the case where the tele end is determined in steps 510 and 511, the in-focus position is detected while moving the variable magnification lens 102 to the wide side, and the wide side reference variable magnification lens position is determined.

At step 512, the position of the zoom encoder at this variable magnification lens position (count value of the stepping pulse number of the stepping motor) is used as the variable magnification lens position of the focus reference value in the ROM in the AF microcomputer 116 or the external E ^2. Programmable and non-volatile memory Vw 'such as PROM
And the focus position here becomes the reference position of the focus lens.

By performing the above processing, the tele end and the focus reference position are determined.

In step 513, the variable power lens 102 is moved to the wide side from Vt '(T' in FIG. 4) stored as the position of the telephoto end by the designed value of magnification (25 mm in actual distance in FIG. 4). Therefore, the magnification as designed is secured. The zoom lens position becomes the wide end (W ″ in FIG. 4).

Next, in step 514, the focus motor 12
1, the focus lens 105 is moved to focus.

In step 515, it is checked whether or not there is focus, and the focus lens 105 is moved until it comes into focus.

When it is confirmed in step 515 that the focus is achieved, in step 516 the focus lens 105 at that time is focused.
The position of is stored in Fw ″ (in FIG. 4) as the focus position at the wide end. This value becomes the wide end reference position.

It is desirable that the telephoto end, the position of the variable magnification lens group at the focus reference position, and the focus lens position at the wide end reference position determined above are stored in a writable E ² ROM or the like.

As described above, in the present embodiment, even in the rear focus type zoom lens including the variation of the focal length caused by the management of the manufacturing error or the amount of the blur generated in the middle of the zoom, the entire zoom range is achieved. It is possible to realize a lens position control device in which blurring is small and an error in the zoom ratio is small.

(Second Embodiment) In the first embodiment,
Although the tele end of the variable power lens, the variable power lens position of the focus reference value, the focus reference value, the wide end reference position, etc. are determined and the focus of the adjustment subject is determined, one adjustment subject is used. Is.

Therefore, a method of obtaining the in-focus point of another subject distance from the focus adjustment of the first embodiment will be described next.

In FIG. 6, the focus position at the wide end when the magnification of the design value is secured when the adjusted subject distance is infinite is B
It becomes (0 '', 0) (of FIG. 4).

Using this focusing point, for example, a subject distance of 10
When the focus position at the wide end of cm is obtained, design value information that stores the relationship between the focal length and the focus position according to the subject distance is stored in the AF microcomputer 116 of FIG. The infinite design value locus is the line segment A (1,0) -A (0,
0), and the infinite cam locus of the actual lens is the line segment A (1,
Since 0) -B (0 '', 0), the slope is (A (1,0) -A (0,0)) / (z1-z0) → (A (1,0) -B ( 0``, 0)) / (z1-
z0 ''), which is also true for other subject distances.

Therefore, for example, in order to obtain the actual inclination of the lens at a subject distance of 10 cm, from FIG. 6, (A (1,1) -B (1 '', 0)) / (z1-z0 '') ≈ ( (A (1,1) -A (0,1)) / (A
(1,0) -A (0,0))) * ((A (1,0) -B (0 '', 0)) / (z1-z0 '')).

If the tilt is obtained, the in-focus position at W ″ (wide end) with a subject distance of 10 cm can be obtained, and the in-focus position at the wide end is stored only for the subject distance for adjustment. In other words, other subject distances can be calculated even if the design value and the actual trajectory of the lens deviate.

If the in-focus point at the wide end (W ″) is known, the relationship between the in-focus points between the zoom position on the wide side from W ′ to W ″ and the focus position can be calculated.

As described above, according to the present invention, in the focus adjustment, the telephoto end, the zoom lens position of the focus reference position, and the focus lens position of the wide end reference position are determined, and by the above calculation, the focus lens positions other than those during the focus adjustment are calculated. By calculating the in-focus point of the subject distance of, even if a lens having an error with the design cam locus is produced in the production process, it is possible to perform lens control without intermediate focus shift and ensuring a design magnification.

[0083]

As described above, according to the invention described in each claim of the present application, when the distance from the tele end to the wide end determined in the tele middle tracking adjustment is different from the design magnification, By storing and storing the focus value of the subject distance at the wide end when the edge position is shifted to match the design value, even if the lens has a cam locus that deviates from the design value, the magnification of the focal length It is possible to realize the adjustment which satisfies the design value and has no intermediate focus deviation.

Further, when the distance from the tele end to the wide end determined in the tele middle tracking adjustment is different from the design magnification, the object distance at the wide end when the position of the wide end is shifted to match the design value If one focus value is stored and stored, and the focus points of other subject distances are also calculated, even if the lens has a cam locus that deviates from the design value, the magnification of the focal length satisfies the design value. , It is possible to realize lens control without any intermediate focus shift at any subject distance.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a lens control device of the present invention.

FIG. 2 is a diagram showing a configuration of an inner focus type lens.

FIG. 3 is a diagram showing a cam locus showing, for each object distance, the position of the focus lens that maintains the in-focus state with respect to the position of the variable power lens in the inner focus type lens.

FIG. 4 is a diagram for explaining a relationship among a constant stroke adjustment, a tele-middle tracking adjustment operation, and a focus lens position error.

FIG. 5: AF microcomputer 11 when focus adjustment is performed
6 is a flowchart showing a processing operation within 6.

FIG. 6 is a diagram for explaining a lens adjusting method according to a second embodiment of the present invention.

[Explanation of symbols]

 102 variable magnification lens 105 focus lens 106 image sensor 108 camera signal processing circuit 115 AF evaluation value processing circuit 116 AF microcomputer 118 zoom driver 119 zoom motor 120 focus driver 121 focus motor 123 zoom SW unit

Claims (4)

[Claims] 1. A first lens group for performing a zooming operation, a second lens group for correcting the movement of a focal plane when the first lens group moves, and the first and second lens groups. Driving means for independently moving the lens groups in parallel with the optical axis, detecting means for independently detecting the first and second lens group positions, and second detecting means for the first lens group positions. A storage unit that stores the in-focus position of the lens group according to the subject distance, the positions of the first lens group at the wide side, the tele side, and the intermediate point at a predetermined subject distance, and the first lens group From the information on the in-focus position of the second lens group at each set position, the telephoto end of the first lens group and the second
Control means for setting a reference position of the lens group, setting a wide end with the tele end as a reference, and storing a focus position at the wide end as a wide end reference position of the second lens group. A lens control device characterized in that 2. The information according to claim 1, wherein the control unit stores information on a focus position of the second lens group with respect to a position of the first lens group according to a subject distance, and the first lens group. And a wide end reference position of the second lens group, a focus position on the wide side according to the subject distance is calculated. 3. A lens control device comprising a first lens group for performing a zooming operation, and a second lens group for correcting the movement of the focal plane when the first lens group moves. A lens position adjusting method, comprising setting three positions of the first lens group at least at a wide side, a tele side and an intermediate point at a predetermined object distance, and setting the three positions of the first lens group respectively. The in-focus position of the second lens group at each position is detected, and the telescopic position of the first lens group is determined from the information of the set position of the first lens group and the in-focus position of the second lens group. An end and a reference position of the second lens group are set, a wide end is set with the tele end as a reference, and a focus position of the second lens group at the wide end is set to a wide position of the second lens group. Characterized by the end reference position Lens position adjustment method of the lens control apparatus. 4. The information according to claim 3, wherein the focus position of the second lens group with respect to the position of the first lens group is stored according to a subject distance, and
A lens position adjusting method for a lens control device, which calculates a focus position on the wide side according to a subject distance from the wide end position of the second lens group and the wide end reference position of the second lens group. .