JPH04367809A - Camera system - Google Patents

Abstract

PURPOSE:To obtain the camera system with high optical performance by utilizing a program for correcting a defocusing quantity due to zooming when performing the zooming operation according to inputted zooming position information. CONSTITUTION:A process part 108 finds the positions of respective lens groups on the optical axis according to zoom position information which is inputted from a zooming operation member 110 by utilizing a memory part 109 wherein a program for calculating the positions of the respective lens groups on the optical axis is recorded and driving parts 104a and 104b drive the respective lens groups; and position detection parts 105a and 105b detect the current positions of the respective lens groups on the optical axis and lens position control means 107a and 107b use two pieces of position information obtained by the process part and position detection part to control the driving of the respective lens groups by using the driving parts. At this time, the program recorded in the memory part is prepared inherently to each zoom lens.

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 must 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 extremely 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 during zooming by electrical means without using a cam groove, and also controls the actual optical axis of each lens group during zooming. The entire magnification range can be adjusted by detecting the upper position and correcting the variation in the amount of deviation of the focus position caused by the position error from the set value using a program or correspondence table recorded in advance in the memory section. The purpose of the present invention is to provide a camera system that can obtain good images that are in focus over a wide range of areas.

[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 or zoom position that uses a processing unit to calculate the position on the optical axis of each lens group at the zoom position based on zoom position information input from a zooming operation member. The position of each lens group on the optical axis is determined by using a memory unit that records at least one of the following: and a correspondence table showing the positional relationship of each lens group on the optical axis, and the output signal from the processing unit is Based on this, each lens group is driven by the drive unit, the position of each lens group on the optical axis at this time is detected by the position detection unit, and the two position information obtained by the processing unit and the position detection unit are When controlling the drive of each lens group by the lens position control means using the drive unit, the program or correspondence table recorded in the memory unit for the correction lens group is unique and created for each zoom lens. It is characterized by

In particular, in the present invention, the program or correspondence table recorded in the memory section for the correction lens group contains positional information for correcting the amount of focus deviation caused by manufacturing errors when changing the magnification with the correction lens group. The feature is that it is calculated.

[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 109 denotes a memory unit in which arithmetic expressions for calculating positional information (for example, relative position from a reference position at the wide-angle end, etc.) of each of the moving lens groups 101a and 101b are programmed and stored.

That is, an arithmetic program for calculating positional information of each lens group 101a, 101b during zooming in the processing section 108 is stored. For example, in a calculation program that calculates the position information of a lens group that corrects the amount of focus shift that occurs when changing the magnification, data that has been obtained by measuring the amount of focus shift that occurs due to zooming for each zoom lens is used. Based on this, an arithmetic program for calculating the positional information of the lens group for correcting this amount of deviation is determined and stored.

Note that instead of such a program, the memory unit 109 stores a correspondence table showing the positional relationship of each lens group on the optical axis at each zoom position, and extracts and uses it based on the zooming position information. You can do it like this.

The processing section 108 includes a zooming operation member 110
The position of each lens group on the optical axis is calculated from the zooming position information from the camera and the calculation program stored in the memory unit 109, and is mainly composed of a 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, uses the calculation program in the memory unit 109, and adjusts the lens group 101.
The position of a on the optical axis is calculated, and the position information is input to the lens position control means 107a.

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, in step 2 the processing unit 108
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 memory unit 109.

Then, in step 4, the position information of each lens group on the optical axis is transmitted to lens position control means (107a, 107b).
Output to. In step 5, the lens position control means (107
a, 107b) detects the current position information on the optical axis of each lens group handled by the lens position control means.
a, 105b). In step 6, the difference between the position information previously output from the processing unit 108 and the current position information is determined. In step 7, 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 8, and the operation from step 5 is repeated. When the difference becomes 0, it is determined that zooming has finished, and the operation returns to step 1.
Prepare for the next zooming operation.

Next, the arithmetic program stored in the memory section 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.

[0027]

[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 ´

[0028]

[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 ‥‥‥‥‥‥‥■. Also, depending on the correction state of lens aberrations, the state of the diaphragm often causes out of focus, so it is also possible to rewrite the parameters of equation (2) by adding parameters related to the diaphragm.

For each zoom lens, the amount of focus deviation is measured in advance. Then, this amount of focus shift is replaced by an approximate expression using zooming position information (here, focal length) as a parameter.

ΔI=h(fT) ‥‥‥‥
‥‥‥■However, if ΔI is the paraxial vertical magnification determined by all lens groups on the image plane side of the focus deviation correction lens group, then α is one formula for determining the position of the correction lens group. It is calculated by setting L'=L-α·ΔI ‥‥‥‥‥‥‥■'. When measuring the amount of out-of-focus, taking into account the state of the aperture, an approximate equation can be created by adding parameters related to the state of the aperture to equation (2). The above-mentioned arithmetic expressions are programmed and stored in the memory section. As a result, each zoom lens is highly accurately corrected based on the measured value of the amount of defocus.

In this embodiment, the calculation program is stored in the memory section, but as described above, the zooming position information is divided into the necessary number of pieces,
A correspondence table for calculating position information may be stored and used. For example, instead of using an arithmetic formula to calculate the amount of focus deviation using focal length as a parameter, use a correspondence table between the focal length and the amount of focus deviation, and then convert it to position information into an arithmetic program. It may be possible to store both correspondence tables.

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, when actually measuring the amount of focus deviation for each zoom lens, the arithmetic program or correspondence table stored in the memory section was used at the design stage to take into account the obvious fluctuations in spherical aberration due to zooming. It is desirable that the amount of focus deviation caused by this is corrected. This is because this amount is large compared to the allowable amount of focus deviation and becomes a factor that increases measurement errors. Further, this is because when attempting to perform highly accurate correction, many measurement points are required, which increases the order of the approximation equation and increases the number of data in the correspondence table.

[0038]

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. Detects the actual position of each lens group on the optical axis, and uses a program or correspondence table stored in advance in the memory to measure the variation in focus position deviation caused by position error from the set value at this time. By making the correction, 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, at the manufacturing stage of the zoom lens, the amount of focus deviation for each zoom lens is actually measured, and based on that data, the calculation program to be stored in the memory section is rewritten, thereby achieving high precision focusing. The result is a zoom lens that corrects the amount of misalignment. Also, since only the memory section can be modified to accommodate each individual lens,
It has the advantage of being able to improve the performance of zoom lenses without increasing costs.

[Brief explanation of the drawing]

[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 109 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. A program for calculating the position of each lens group on the optical axis at the zoom position by a processing unit based on zoom position information input from a zooming operation member, or a positional relationship between the zoom position and each lens group on the optical axis in a camera system having The position of each lens group on the optical axis is determined using a memory unit that records at least one of the correspondence table showing At this time, the position of each lens group on the optical axis 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 control each lens group. A camera system characterized in that, when controlling the drive using the drive unit, a program or a correspondence table recorded in the memory unit for the correction lens group is unique to each zoom lens. 2. The program or correspondence table recorded in the memory unit for the correction lens group is for calculating positional information for correcting the amount of focus deviation caused by manufacturing error when changing the magnification with the correction lens group. The camera system according to claim 1, characterized in that: 3. The program or correspondence table recorded in the memory section is for calculating positional information of each lens group for correcting the amount of focus shift when changing the magnification. Camera system in item 1.