JPH04367812A - Camera system - Google Patents

Abstract

PURPOSE:To obtain the camera system which perform zooming operation with high accuracy according to zooming position information inputted from outside. CONSTITUTION:A program which calculates the positions of respective lens groups on the optical axis at respective zoom positions is recorded in a 1st memory part 109a and a program which calculates the positions of a correcting lens group on the optical axis so as to correct a defocusing quantity characteristic to a manufacture error is recorded in a 2nd memory part 109b; and a process part 108 finds the positions of the respective lens groups on the optical axis by utilizing the 1st and 2nd memory parts and a position detection part detects the positions on the optical axis when the respective lens groups are driven. Then lens position control means 107a and 107b control the driving of the respective lens groups by using position information obtained by a process part and the position detection part.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a camera system.
For example, when a mechanism is provided in which each lens group is moved by an independently provided drive unit for zooming, and each lens group is moved to change the magnification based on zoom position information input from a zooming operation member, The present invention relates to a camera system suitable for television cameras and the like that requires high optical performance, which corrects variations in the amount of focus shift during magnification changes due to manufacturing errors.

0002

2. Description of the Related Art Conventionally, in camera systems such as television cameras, a mechanical cam ring is used to move a lens group for zooming. This cam ring is formed with cam grooves corresponding to each lens group that moves during zooming. Zooming is performed by using this cam groove to mechanically control the relative position in the optical axis direction of the lens group that moves during zooming.

FIG. 4 is a schematic diagram showing the paraxial refractive power arrangement of a conventional zoom lens consisting of four lens groups. In the figure, the first group (F
), the second group (V) mainly performs magnification, the third group (C) mainly corrects the image plane that changes with magnification, and the fixed image forming group during zooming and focusing. 4th group (R
) shows a so-called 4-group zoom lens consisting of four lens groups.

In the figure, I indicates the image point of the entire lens system. The second group V moves on a solid line J1 during reciprocating zooming between the wide-angle end (W) and the telephoto end (T). In conjunction with this, the third group C moves on the solid line J2. At this time, the position of the image point I is always fixed during zooming, and as a result, the image point is located on the straight line J3, that is, on the photosensitive surface. The movement locus of the second group V and the third group C becomes the locus of the cam groove cut in the cam ring, and the reference focal length (for example, W
At the end), the relative positions of the four lens groups are adjusted, thereby forming a zoom lens.

[0005]

[Problem to be Solved by the Invention] If there is a manufacturing error in the cam groove for moving the lens group for variable magnification as described above,
The relative positions of the moving lens groups (third group C and second group V) in the optical axis direction deviate from the designed ideal relative positions in the optical axis direction. If the amount of deviation at this time is always constant during zooming, then by correcting the relative position of the cam groove and the lens group by the amount of deviation, the focus position during zooming can be corrected to a constant position. can.

However, if the movement locus of the third group C in FIG. 4 changes as shown by the broken line J2' in the relative position of the third group C and the second group V during zooming, however, the image point I
For example, the position of the broken line J cannot be fixed during zooming.
It changes like 3'. Since the amount of deviation in relative position changes due to zooming, the amount to be corrected also changes during zooming, and the image plane cannot be maintained at a constant position unless the amount of correction is changed in accordance with zooming. Generally, it is very difficult to perform such correction using a mechanical cam ring.

A similar problem also occurs due to manufacturing errors in the focal length of each lens group constituting the zoom lens. Manufacturing errors in the focal length of the first group F and fourth group R, which are fixed during zooming, can be corrected by correcting the relative positions of those lens groups so that the focus position is always fixed during zooming. Can be done.

However, if there is a manufacturing error in the focal length of the second group V or the third group C, which move during zooming, the amount of correction of their relative positions will change during zooming, so this will need to be corrected. It is very difficult to do so.

In particular, as cameras become more sophisticated, as exemplified by recent high-definition television cameras, the zoom lenses used therein need to minimize changes in focus position due to zooming. . For this purpose, the relative position accuracy of the lens groups that move during zooming must be made very strict. This is extremely difficult to do with conventional mechanical control using a cam ring, as it is not possible to correct manufacturing errors of individual zoom lenses.

The present invention controls the drive of at least one lens group among the lens groups to be moved by changing magnification by electrical means without using a cam groove, and also by controlling the drive of at least one lens group among the lens groups to be moved by changing magnification. Detects the first memory section that stores the program to find the positional information and the actual position of each lens group on the optical axis, and corrects for fluctuations in the amount of deviation in the focus position caused by positional errors from the set values at this time. It is an object of the present invention to provide a camera system capable of obtaining a good image in focus over the entire magnification range by using a second memory section in which a program or a correspondence table is recorded.

[0011]

[Means for Solving the Problems] The camera system of the present invention has at least two lens groups, a variable magnification lens group and a correction lens group for correcting an image plane that varies due to variable magnification, each having an optical axis driven by an independent drive unit. In a camera system having a zoom lens that is moved upward to change magnification, a program that calculates the position of each lens group on the optical axis at each preset zoom position, or a positional relationship between the zoom position and each lens group on the optical axis. At least one of the correspondence table showing At least one of a program for calculating the position on the axis or a correspondence table indicating the positional relationship between the zoom position and the optical axis of the correction lens group is recorded in a second memory section, and zoom position information input from the zooming operation member. Based on this, the processing unit uses the first memory unit and the second memory unit to determine the position of each lens group on the optical axis, and the drive unit moves each lens based on the output signal from the processing unit. The lens groups are driven, the position of each lens group on the optical axis at this time is detected by the position detection section, and the lens position control means uses the two pieces of position information obtained by the processing section and the position detection section to determine the position of each lens group on the optical axis. It is characterized in that the lens group is driven and controlled using the drive unit.

Particularly, the present invention is characterized in that the program or correspondence table recorded in the first memory section is corrected for the amount of focus shift caused by fluctuations in spherical aberration due to zooming in the design stage.

[0013]

[Example] Figure 1 is a schematic diagram of the main parts of Example 1 of the present invention, Figure 2
2 is a block diagram of the main parts of FIG. 1. FIG. 101a, 101 in the figure
b are lens groups that move during zooming, for example, the lens group 101a is a variable magnification lens group, and the lens group 101a is a variable magnification lens group;
b is a correction lens group that corrects the image plane that fluctuates due to zooming.

The lens group 101a (101b) is assembled into a lens barrel 102a (102b) which is threaded on the outside. Although the lens barrel 102a (102b) is not shown in the figure, it has a structure that allows it to move back and forth in a straight line along the optical axis of the lens group. Lens barrel 102a (
102b) is the straight gear 103a (103b).
The linear gear 103a (103
b) rotates, the lens group 101a (101
b) moves on the optical axis. Straight gear 103a (103b)
One end of the linear gear 103a (103b) is directly connected to the rotating shaft of the motor 104a (104b) as a drive unit by a coupling member 106a1 (106b1), and the other end of the linear gear 103a (103b) is position-detected by a coupling member 106a2 (106b2). Potentiometer 105a (105b
) is directly connected to the rotating shaft.

Reference numeral 110 denotes a zooming operation member, which adjusts the lens groups 101a and 10 based on the input zoom position information.
Zooming position information for moving 1b is output to the processing unit 108. The zooming operation member 110 has a position and a focal length of 1, such as a potentiometer, for example.
The focal length may be output as zooming position information in a one-to-one correspondence.

Reference numeral 109a denotes a first memory section, which stores an arithmetic program for calculating the positional information of each lens group based on, for example, the focal length of each lens group and the distance between lens groups determined at the design stage. ing.

The calculation program for calculating the positional information of the correction lens group 101b of this embodiment is based on the amount of focus deviation caused by the influence of spherical aberration that changes due to zooming and the state of the aperture value of the diaphragm, which is obvious at the design stage. Corrects changes in focus, etc. Reference numeral 109b is a second memory unit that actually measures the amount of focus shift for each zoom lens due to manufacturing errors in the focal length of lens groups and the spacing between lens groups, which are not clear at the design stage, and stores the data based on the data. The amount of correction movement of the correction lens group is uniquely determined and stored as a program or a correspondence table of the amount of movement with respect to the focal length.

Reference numeral 108 denotes a processing unit which uses zooming position information obtained from a zooming operation member 110, which will be described later, and calculation programs and correspondence tables in the first memory unit 109a and second memory unit 109b to calculate information on the optical axis of each lens group. It calculates the position and is mainly composed of the CPU.

Lens position control means 107a and 107b control the position of each lens group on the optical axis based on the position on the optical axis of each lens group calculated by the processing unit 108 and the position on the optical axis of each lens group obtained from the potentiometers 105a and 105b. The position of each lens group on the optical axis is controlled by drive units 104a and 104b.

The operation will now be explained using the lens group 101a as an example. When a person operating the zoom lens inputs zoom position information using the zoom operation member 110, the zoom position information, such as focal length, is input from the zoom operation member 110 to the processing unit 108. The processing unit 108 receives the zooming position information and
Using the calculation program in the memory section 109a and the correspondence table in the second memory section 109b, the position of the lens group 101a on the optical axis is calculated, and the position information is transmitted to the lens position control means 10.
7a.

On the other hand, the rotation angle of the linear gear 103a has a one-to-one correspondence with the movement of the lens group 101a.
Potentiometer 105a which is the position detection means of 01a
The lens position control means 107 uses the voltage corresponding to the rotation angle of the linear gear 103a as the position information of the lens group 101a.
I am inputting it to a. The lens position control means 107a converts the signal (voltage) obtained from the position detection section 105a into position information of the lens group. The difference between the position information at this time and the position information on the optical axis of the lens group 101a obtained from the position detection unit 105a is determined. If the difference between the two positional information is not 0 (or approximately 0), the lens position control means 107a supplies power to the motor 104a, and drives the lens group 101a through the linear gear 103a directly connected to the motor 104a. Then, the position of the lens group on the optical axis is changed so that the difference between the two positional information becomes 0. Similarly, the position of the lens group 101b on the optical axis is changed according to the operation of the zooming operation member 110.

Next, the operation of this embodiment will be explained using the flowchart of FIG.

In step 1, it is determined whether a zooming operation has been performed using the zooming operation member. If it has not been performed, step 1 is repeated after a certain period of time (which is so short that the operator cannot notice it), and if it has been performed, processing unit 108 returns to step 2.
reads zooming position information from the zooming operation member. When this is completed, in step 3, the processing unit 108 calculates position information on the optical axis of each lens group corresponding to the target focal length according to the calculation program stored in the first memory unit 109a.

[0024] Then, in step 4, the second memory section 109
The position correction information of the correction lens group calculated above is calculated from the correspondence table stored in b. In step 5, the positional information of the corrective lens group is determined by adding the positional correction information calculated in step 4 to the positional information on the optical axis of the corrective lens group calculated in step 3.

In step 6, the position information of each lens group on the optical axis is output to the lens position control means (107a, 107b). In step 7, the lens position control means (107a, 1
07b) is a position detecting unit (105a, 1
05b). In step 8, the difference between the position information previously output from the processing unit 108 and the current position information is determined. In step 9, it is determined whether the difference is 0 or not. If the difference is not 0, each lens group is driven so that the difference becomes 0 in step 10, and the operation is repeated from step 7. When the difference becomes 0, it is determined that zooming has ended, and the operation returns to step 1 to prepare for the next zooming operation.

Next, the arithmetic program stored in the first memory section 109a of this embodiment will be explained in detail.

First, the principle of the arithmetic expression used in the arithmetic program of this embodiment will be explained. Lens group 1
The focal lengths of 01a and 101b are fa and fb, respectively.
Let βa and βb be the respective paraxial lateral magnifications at the reference focal length (for example, the zoom position at the wide-angle end). Ignoring the thickness of each lens group, the distance D between each lens group is given by the following equation.

[0028]

[Equation 1] At this time, the positions of the object point and image point are respectively in the lens group 1
Distance S1 from 01a, distance Sk from lens group 101b
Suppose it is at a distance of ´

[0029]

[Equation 2] The distance L between the object and image points is L=-S1 +D+Sk' (=constant) ‥‥‥
‥■ becomes.

Next, it is assumed that the lens group 101b is used as a correction lens group for correcting the image plane, and that the lens group 101a moves along a trajectory determined at the time of design to change the distance S1. At that time, the paraxial lateral magnification βa can be obtained from the formula ■, so
The distance Sk' is determined from the formulas ■, ■, and ■, and the amount of variation from the distance Sk' at the reference focal length is the lens group 101b.
is the amount of movement from the reference focal length. Here the distance Sk
' is a quadratic root, but since you have decided which root to use at the time of design, you can choose a solution based on that. If these equations are combined into a single relational equation gb in which the focal length of each lens group is used as an input parameter of the calculation equation, it will be as shown below.

Mb = gb (Ma, fa, fb)
‥‥‥‥‥‥‥■ However, Ma and Mb are lens groups 101a and 101b
The amount of movement from the reference focal length of .

Since the movement amount Ma changes due to zooming, it is rewritten in accordance with the zooming information obtained. For example, the amount of movement Ma is the focal length of the entire system fT
Since they are connected by a certain relational expression, change the parameters of formula (①) from the amount of movement Ma to fT and get Mb = gb ′ (fT , fa , fb )
It can be rewritten as ‥‥‥‥‥‥‥■.

In this embodiment, by subtracting the amount of focus deviation due to the aforementioned spherical aberration and the condition of the aperture of the diaphragm from the equation (2), the calculation formula corrects the amount of focus deviation that is obvious at the design stage.

Next, the correspondence table stored in the second memory section 109b of this embodiment will be described. First, all 0s are entered as correction amounts in the correspondence table stored in the second memory section 109b of the target zoom lens. In this state, only the amount of focus deviation due to the spherical aberration determined at the design stage and the state of the aperture of the diaphragm is corrected, so the amount of focus deviation due to manufacturing errors cannot be eliminated. Using this zoom lens, the amount of focus shift due to actual zooming and the state of the aperture aperture is measured at each focal length.

On the other hand, a table of sensitivity (ratio of focus movement amount to the correction lens group) at each focal length of the correction lens group is prepared using design values.

Determine the amount of correction at each focal length position of the target zoom lens using the above-mentioned measured values and sensitivity table, obtain a correspondence table between focal length and amount of correction, and store it once in the second memory section 109b. Store.

Then, the amount of focus deviation due to zooming is actually measured again to determine the amount of correction, which is added to the previous correspondence table. By repeating this process several times until the amount of defocus falls within the allowable range, you will have a zoom lens that has corrected the amount of defocus with high precision. Naturally, the operations related to the position of the aperture may be added to the above operations.

In this embodiment, what is stored in the first memory section is an arithmetic program, and what is stored in the second memory section is a correspondence table, but even if what is stored in each memory section is a computation program, it is compatible. It may be a table,
It can be both. For example, the correspondence table between focal length and correction amount stored in the second memory section is
It is also possible to create an approximate formula for determining the amount of correction using the focal length as a parameter, program it, and store it.

Further, in this embodiment, a linear gear and a rotary motor are used to move the lens in a straight line, but a linear cam, a helicoid, a linear motor, etc. may be used to move the lens in a straight line. Furthermore, an actuator using a piezoelectric element or the like may be used instead of the motor.

Although the coupling member is used to directly connect the motor and the rotary shaft of the potentiometer, it may be used to provide a difference in rotation using a gear or the like. A rotary encoder, a linear encoder, or the like may be used instead of a potentiometer as a position detection section.

In this embodiment, the arithmetic program or correspondence table stored in the first memory section is corrected based on the amount of focus shift caused by fluctuations in spherical aberration due to zooming, which is already clear at the design stage. By using , it is possible to avoid a very large amount of defocus in a zoom lens that is controlled by the position information of the lens group calculated only in the first memory section, and to keep the amount of correction of the correction lens group small. This is preferable because it can be done.

Furthermore, this makes it possible to easily create an arithmetic program and a correspondence table for calculating the amount of correction for the correction lens group. In other words, if it is an approximate expression to be used as an arithmetic program,
It can be a simple approximation formula with a low degree, and if it is a correspondence table, the number of memories can be reduced. or,
It has the advantage of being able to reduce the number of measurement points.

Furthermore, if the amount of correction of the correction lens group is calculated using actual measured values such as the focal length and lens spacing of at least the moving lens group of the target zoom lens, the amount of focus deviation can be minimized. is possible.

[0044]

According to the present invention, as described above, at least one lens group among the lens groups to be moved by changing the magnification is controlled by electric means without using a cam groove, and the movement of the lens group is controlled by electric means without using a cam groove. The first memory section stores a program to obtain the positional information required from the design of each lens group, and the actual position of each lens group on the optical axis is detected, and the focus position resulting from the positional error from the set value at this time By using a program for correcting variations in the amount of shift or a second memory section storing a correspondence table, it is possible to achieve a camera system that can obtain good, well-focused images over the entire magnification range.

In particular, in the present invention, in the manufacturing stage of the zoom lens, the amount of focus shift for each zoom lens is actually measured, and based on the data, the calculation program or correspondence table to be stored in the second memory section is rewritten. This creates a zoom lens that corrects the amount of focus deviation with high precision. Furthermore, since only the memory section is changed to correspond to each individual lens, it has the advantage that the performance of the zoom lens can be improved without increasing costs.

[Brief explanation of drawings]

[Figure 1] Schematic diagram of main parts of Example 1 of the present invention

[Figure 2]
Block diagram of main parts in Figure 1

[Figure 3] Flowchart showing the operation of the present invention

[Figure 4
] Explanatory diagram of the paraxial power arrangement of a general 4-group zoom lens

[Explanation of symbols]

101a, 101b Lens groups 102a, 102b Lens barrels 103a, 103b Straight gears 104a, 104b Drive sections 105a, 105b Position detection sections 106a, 106b Coupling members 107a, 107b Lens position control means 108
Processing section 109a First memory section 109b Second memory section 110 Zooming operation member

Claims (3)

[Claims] 1. A zoom lens that changes magnification by moving at least two lens groups, a variable magnification lens group and a correction lens group that corrects an image plane that has changed due to magnification changes, on the optical axis using independent drive units. In a camera system having a camera system, at least one of a program for calculating the position on the optical axis of each lens group at each preset zoom position or a correspondence table showing the positional relationship between the zoom position and the optical axis of each lens group is provided as a first step. 1 A program or zoom position that calculates the position on the optical axis of the correction lens group to correct the amount of focus deviation inherent to manufacturing errors when moving each lens group due to zooming while recording in the memory section and a correspondence table showing the positional relationship of the correction lens group on the optical axis in a second memory section, and the processing section records at least one of the correspondence table showing the positional relationship on the optical axis of the correction lens group, and the processing section records the zoom position information inputted from the zooming operation member in the first memory section. The position of each lens group on the optical axis is determined using the second memory section, and each lens group is driven by the drive section based on the output signal from the processing section. The position on the optical axis of the lens is detected by the position detection section, and the two position information obtained by the processing section and the position detection section are used to drive each lens group by the lens position control means using the drive section. A camera system that is characterized by: 2. The camera according to claim 1, wherein the program or the correspondence table recorded in the first memory section has been corrected for an amount of focus shift caused by fluctuations in spherical aberration due to zooming in the design stage. system. 3. The program or correspondence table recorded in the second memory unit for the correction lens group calculates positional information for correcting the amount of focus deviation caused by manufacturing error when changing magnification with the correction lens group. 2. The camera system of claim 1, wherein the camera system is unique to the camera system.