JPH04335313A - Camera system - Google Patents

Abstract

PURPOSE:To obtain a camera system in which the position of a lens group for focusing on an optical axis in a rear focus system zoom lens is calculated to be obtained at a high speed by using a coefficient stored in a memory means. CONSTITUTION:In the camera system provided with the rear focus system zoom lens SL, a corresponding moving coefficient is selected from the memory means 11 where the moving coefficients of the respective lens groups 8a-8c with respect to focal length information and object distance information inputted from the outside are respectively recorded, and the positions of the lens groups on the optical axis are calculated by an arithmetic means by using the moving coefficient, then the lens groups 8a-8c are moved by lens driving means 9a-9c based on a signal from the arithmetic means.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION The present invention relates to a camera system suitable for television cameras, video cameras, 35mm film photographic cameras, etc., and particularly to a camera system that includes a plurality of lens groups that are independently movable during zooming and focusing. The present invention relates to a camera system having a rear focus zoom lens.

0002

[Prior Art] Zoom lenses conventionally used in television cameras, video cameras, photographic cameras, etc. employ a so-called rear focus type in which focusing is performed by moving lens groups other than the first lens group on the object side. Various methods have been proposed.

In general, rear focus type zoom lenses have a smaller effective diameter of the first group than zoom lenses that focus by moving the first group, making it easier to downsize the entire lens system, and making it easier to take close-up shots. In particular, very close-up photography is facilitated, and since this is done by moving a relatively small and lightweight lens group, the driving force for the lens group is small and quick focusing is possible.

FIG. 5 shows a part of the lens group 55 or all the lens groups 5 of the relay lens 53 located behind the conventional variable power system.
FIG. 3 is an optical schematic diagram of a so-called rear focus type zoom lens in which focusing is performed by moving lens 3;

In FIG. 5, lens group 51 and lens group 54
(R) is fixed, and the lens group 52 (V) as a variator changes its position in the optical axis direction by adjusting the focal length. Also, part of the lens group 55 (RR
The lens) has the role of both correcting image plane fluctuations during zooming and adjusting focus.

In the zoom lens shown in FIG. 5, FIG. 6 shows the position of the lens group 52 (V) on the horizontal axis, that is, the variable power position, and the vertical axis shows the position of the lens group 55 (RR lens) on the optical axis during focusing. It is an explanatory view when the position is taken.

In the lens configuration shown in FIG. 5, it is necessary to change the position of the lens group 55 (RR lens) on the optical axis both when the subject distance changes and when the focal length (zoom position) of the zoom lens changes. .

Such a rear focus type zoom lens has been proposed, for example, in Japanese Patent Publication No. 52-15226. In this publication, the positions on the optical axis of the zoom lens group and the focus lens group, which also functions as a compensator, are detected by a detection means when zooming is performed. Next, based on the positional information of both lens groups at this time, the calculation means calculates the position on the optical axis of the focusing lens group that is in focus. The authors have also proposed a zoom lens in which the focus lens group is driven and controlled by a motor or the like based on the results of this calculation.

Furthermore, in Japanese Patent Application Laid-Open No. 143309/1982, the positions on the optical axis of a variator lens group and a compensator lens group having a focus function are stored in a storage means in relation to the position of the variator lens group. . A zoom lens is proposed in which the position of the compensator lens group is read out by a storage means in accordance with the position of the variator lens group, and the compensator lens group is driven and controlled.

0010

[Problem to be Solved by the Invention] Generally, in a rear focus type zoom lens, the position of the focusing lens group on the optical axis varies depending on the zooming even if the object distance is constant, as shown in Fig. 6, for example. It's coming. For this reason, it is important to drive and control the focusing lens group with high precision and high speed as the magnification changes.

In the zoom lens proposed in Japanese Patent Publication No. 52-15226, the processing time is reduced because the position on the optical axis of the focusing lens group is determined by calculation from the position information of each lens group after the magnification is changed. tended to be longer.

The zoom lens proposed in Japanese Patent Application Laid-Open No. 60-143309 detects the position of a variator lens group, and then reads target information from lens position information stored in a recording means based on the position information. Because of the processing, the time to focus tended to be longer. Furthermore, there is a problem in that the position of the focusing lens group remains constant within a certain range of focal length and object distance of the zoom lens, which deteriorates the accuracy of the lens position. There is also the problem that in order to improve positional accuracy, the amount of storage in the storage means must be increased.

The present invention provides a focal point system in which the position of the focusing lens group on the optical axis is stored in memory means in advance based on the setting value inputted from the focal length setting means, the object distance setting means, or both setting means. The object of the present invention is to provide a camera system that calculates and determines distance using coefficients related to distance and object distance, and thereby can drive and control a focusing lens group at high speed and with high precision using a storage means with a small capacity.

[0014]

[Means for Solving the Problems] The camera system of the present invention changes the magnification by moving a variable magnification section consisting of a plurality of lens groups on the optical axis, and includes at least some of the lens groups of the variable magnification section. In a camera system having a zoom lens in which focusing is performed by moving a focus unit made up of a plurality of lens groups on the optical axis, focal length information is obtained from a focal length setting means and/or object distance information is obtained from an object distance setting means. input, the detection means detects the focal length information and object distance information, and the calculation means records position coefficients of each lens group for the focal length information and object distance information based on the detection signal from the detection means. selecting a corresponding position coefficient from the memory means, calculating the position of each lens group on the optical axis using the position coefficient, and moving each lens group by a driving means based on a signal from the calculation means. It is characterized by

In addition, in the present invention, the focusing section has at least one fixed lens group during zooming, and the zooming section has at least one fixed lens group when focusing. The position of each lens group on the optical axis is represented by several approximate curved surfaces with focal length information and object distance information as variables, and the position coefficient is set from the coefficient representing the approximate curved surface. , and the position of each lens group on the optical axis is represented by an approximate plane using focal length information and object distance information as variables, and the position coefficient is set from a coefficient representing the approximate plane.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram of a main part of a first embodiment of a camera system according to the present invention. In the diagram, SL is the zoom lens body, CA
is the camera body. The zoom lens SL has three lens groups 8a, 8b, and 8c. During zooming and focusing, at least two of the three lens groups 8a to 8c move independently or in a certain relationship on the optical axis.

Reference numerals 10a to 10c are position detecting sections, which detect the positions of the respective lens groups 8a to 8c on the optical axis and input the position information to the lens position control section 7. Reference numerals 9a to 9c are lens drive units, which drive each lens group 8a to 8c based on a drive signal from the lens position detection unit 7.

Reference numeral 1 denotes a focal length setting means, into which the variable power position information (focal length information) of the zoom lens SL is input. Reference numeral 2 denotes an object distance setting means, into which object distance information is input. A detector 3 detects input information from the focal length setting means 1 and the object distance setting means 2, and inputs the information to the CPU 6 as a calculation means. Reference numeral 4 represents a memory means, which is comprised of a ROM and the like. The memory means 4 stores information about each lens group 8a to 8c for the variable power position and object distance of the zoom lens.
Coefficients (position coefficients) for calculating the position on the optical axis by the CPU 6 are stored.

FIG. 2 shows the coefficients (ai
, j , bi, j , ci, j ). As shown in the figure, in order to calculate the position of each lens group on the optical axis when the focal length and object distance are taken as variables, the x-axis shows the focal length (variable magnification position), and the y-axis shows the object distance. is shown. Then, both are divided into a plurality of regions, and coefficients are stored for each region. 5 is ROM containing the program
It is.

The CPU 6 selects focal length information and object distance information from the detector 3 and predetermined coefficients from the memory means 4, and uses these values to program the position of each lens group 8a to 8c on the optical axis. It is calculated and calculated based on. The calculation results are then input to the lens position control section 7. The lens position control section 7 drives and controls the lens drive sections 9a to 9c to move each lens group 8a to 8c to a predetermined position. Thereby, the zoom lens SL is driven and controlled based on the input information from the focal length setting means 1 and the object distance setting means 2.

FIG. 4 is a schematic diagram showing the position on the optical axis of one lens group constituting the zoom lens SL that moves during focusing in terms of the magnification change position (focal length) and object distance.

In the figure, the x-axis shows the magnification change position (focal length),
The object distance is shown on the y-axis, and the position of the lens group on the optical axis is shown on the z-axis. That is, the z-axis direction corresponds to the optical axis direction of the zoom lens. INF indicates infinity, MOD indicates close range, WIDE indicates wide-angle end, and TELE indicates telephoto end.

As shown in the figure, in the zoom lens according to the present invention, the position (z) of the lens group on the optical axis changes non-linearly depending on the variable power position (x) and the object distance (y), and as a whole, is designed to move on one curved surface. Then, one curved surface Sz is expressed as an approximate curved surface, and the coefficients at this time are expressed as coefficients a, b,
It is recorded in the memory means as c.

In this embodiment, the approximate curved surface Sz is treated as an approximate plane for the sake of simplicity. The position Z of the lens group on the optical axis at this time is the focal length x, object distance y,
It can be treated as one point on the plane Sz with coefficients a, b, and c, Z=ax+by+c (1)
It is expressed by the following formula.

Here, x is input from the focal length setting means 1 in FIG. 1, y is input from the object distance setting means 2, and coefficients a, b
, c are stored in the memory means 4 as shown in FIG. 2 according to the values x, y.
The selection is made from one area stored in the . The CPU 6 uses these values to calculate, for example, equation (1) to determine the position (z) of the lens group on the optical axis within the plane area Sz.

In the zoom lens according to the present invention, for example, the three lens groups 8a to 8c move independently during zooming, and the three lens groups 8a to 8c move independently during focusing, or Two lens groups (8a, 8b or 8b, 8c
Alternatively, a lens configuration in which the lenses 8a and 8c) move independently may be used.

In addition, two lens groups (8
a, 8b or 8b, 8c or 8a, 8c) move independently on the optical axis, and during focusing, three lens groups 8a to 8
A lens configuration in which c or two lens groups (8a, 8b or 8b, 8c or 8a, 8c) move independently on the optical axis may be used.

Furthermore, the zoom lens according to the present invention can be similarly applied to a zoom lens composed of two or more lens groups.

Next, the operation of the camera system of this embodiment will be explained using the flowchart shown in FIG.

First, in step 1, the detector 3 detects the presence or absence of a setting signal from the focal length setting means 1, the object distance setting means 2, or both setting means. If there is no setting signal, it waits for the setting signal, and if there is, the setting value signal (x, y) detected by the detector 3 is output from the detector 3. In step 2, the CPU 6 receives the set value x from the detector 3,
Read y. In step 3, the CPU 6 reads coefficients (a, b, c) related to the set values x and y for each lens group from the memory means 4 in which coefficients are stored for each lens group, as shown in FIG. 2, for example.

Here, the relationship between the set values x, y and the coefficients a, b, c is as shown in FIG. On the other hand, the lens position z is calculated using the coefficients (a, b, c) corresponding to the area S1 as follows: z=a×x+b×y+c.

The coefficients a, b, c read out in step 4
The above calculation is performed using the set values x and y to determine the lens position z. In step 5, the lens position signal z is output to the lens position control section 7. In step 6, the lens position controller 7 detects the current position of the lens group using the position detector (10).
) and find the difference between the lens position signal and the current position. In step 7, the above difference is determined, and if the difference is 0, the system waits for a set value signal, and if the difference is not 0, a drive signal that makes the difference 0 is output.

In step 8, the lens driving section 9 drives the lens group. Then, return to step 6 and repeat the above operation until the difference becomes zero. Although the flowchart of FIG. 3 described above shows only one lens group, a similar flowchart exists for each lens group from step 3 onwards. Furthermore, the memory means shown in FIG. 2 also exists for each lens group.

As shown in FIG. 4, the position of the lens group on the optical axis is represented by a curved surface, but in this embodiment, the position of the lens group on the optical axis is approximated by a plane. On the other hand, the position z of the lens group is approximated by a curved surface such as a quadratic surface, and the coefficients thereof are stored in the memory means, and the position of the lens group is determined using the coefficients in the same manner as in the above embodiment. The same effect can be obtained by calculating.

Furthermore, in the above embodiment, the position of the lens group is approximated by several curved surfaces with the object distance and focal length as variables, and the coefficients of the approximated curved surfaces at this time are stored in the memory means, and the coefficients are used as the basis. The position of the lens group was found in , but it is possible to approximate the position of the lens group by some curved surface whose variables are the object distance and the position of the other moving lens group, or to approximate the position of the lens group with the focal length and other moving lens groups. A similar effect can be obtained by approximating several curved surfaces using the positions of the lens groups as variables.

[0036]

According to the present invention, the position of the focusing lens group on the optical axis is stored in advance in the memory means based on the set value input from the focal length setting means, the object distance setting means, or both setting means. It is calculated by using the coefficients related to the focal length and object distance that have been set.
In addition, a camera system whose drive can be controlled with high precision can be achieved.

In particular, the position of the lens group is approximated by a curved surface or plane with the object distance and focal length as variables, the coefficients of the curved surface or plane obtained from this are recorded in the memory means, and these coefficients are used to approximate the position of the lens group. By calculating and determining the position, it is possible to achieve a camera system having the features of increasing the speed of calculation and reducing the memory capacity of the memory means.

[Brief explanation of drawings]

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

[Figure 2]
An explanatory diagram of the memory means in FIG. 1

[Figure 3] Flowchart diagram of Embodiment 1 of the present invention

[Figure 4] Explanatory diagram showing the position of lens groups with respect to object distance and focal length

[Figure 5] Schematic diagram of a conventional rear focus zoom lens

[Figure 6] An explanatory diagram showing the position on the optical axis of the focusing lens group of the zoom lens in Figure 5.

[Explanation of symbols]

SL zoom lens body CA Camera body 1 Focal length setting means 2 Object distance setting means 3 Detector 4. Memory means 5 Program 6 CPU 7 Lens position control section 8a-8c Lens group 9a-9c Lens drive section 10a-10c Position detection section

Claims (5)

[Claims] Claim 1: A variable power section made up of a plurality of lens groups is moved along the optical axis to change the power, and a focus section made up of a plurality of lens groups including at least some of the lens groups of the variable power section is moved along the optical axis. In a camera system having a zoom lens that is moved upward for focusing, focal length information is input from the focal length setting means and/or object distance information is input from the object distance setting means, and the detection means inputs focal length information and/or object distance information from the object distance setting means. object distance information is detected, and the calculation means selects a corresponding position coefficient from a memory means in which the position coefficients of each lens group with respect to the focal length information and object distance information are respectively recorded based on the detection signal from the detection means. A camera system characterized in that the position of each lens group on the optical axis is calculated using the position coefficient, and each lens group is moved by a drive means based on a signal from the calculation means. 2. The camera system according to claim 1, wherein the focus section has at least one lens group that is fixed during zooming. 3. The camera system according to claim 1, wherein the variable magnification section has at least one lens group that is fixed during focusing. 4. The position of each lens group on the optical axis is represented by several approximate curved surfaces having focal length information and object distance information as variables, and the position coefficient is set from a coefficient representing the approximate curved surface. The camera system according to claim 1, 2 or 3, characterized in that: 5. The position of each lens group on the optical axis is represented by an approximate plane with focal length information and object distance information as variables, and the position coefficient is set from a coefficient representing the approximate plane. The camera system according to claim 1, 2 or 3.