JPH01134420A - Photographic lens with movable lens group - Google Patents

Abstract

PURPOSE:To limit the quantity of off-axis luminous flux and to obtain a well- balanced light quantity distribution by moving a luminous flux limiting member at right angles to the optical axis when moving the movable lens group at right angles to the optical axis. CONSTITUTION:When the movable lens group V is made eccentric in parallel at right angles to the optical axis, the luminous flux limiting member P is moved in the opposite direction from the moving direction of the movable lens group V on condition that the movable lens group V has positive refracting power. Consequently, one piece of luminous flux can be cut off, so a decrease in optical performance which is caused when the blur of an image is corrected is corrected by using the luminous flux limiting member P. Consequently, the invariably well-balanced light quantity distribution is obtained and an excellent image is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an m-shape lens having a movable lens group, and in particular a method for changing the optical characteristics of a photographed image by moving the movable lens group in a direction perpendicular to the optical axis. The present invention relates to a photographic lens having a movable lens group that maintains a well-balanced light intensity distribution around the screen when changing the light intensity distribution.

(Prior Art) Various methods have been used to obtain predetermined optical characteristics by moving part of a movable lens group of a photographic lens in a direction perpendicular to the optical axis. For example, (a) Unexamined Japanese Patent Publication No. 62-4
In Japanese Patent No. 4707, a movable lens group is moved in a direction perpendicular to the optical axis to correct the pre-image distortion that occurs when photographing from above a moving object such as an on-going car or an airplane.

(b) In many photographic cameras and video cameras,
When performing shift photography to photograph buildings without distortion, a part of the movable lens group of the photographic lens is decentered.

(C): In automatic tracking shooting such as A-shooting, the speed of the subject image is detected by the image sensor, and some movable lens groups are eccentrically driven to prevent the subject from moving on the film surface. There is. This improves drive responsiveness compared to shaking the entire optical system.

(d) To improve the operability of framing, when making fine adjustments to super-telephoto lenses, etc., if you rotate the entire lens system, the screen will move a lot with a small movement, so some movable lens groups are This is done by moving in a direction perpendicular to the optical axis. This aims to improve the operability of framing.

FIGS. 2A and 2B are schematic diagrams of an optical system according to an embodiment in which, for example, image blur is corrected by moving the movable lens group V in a direction perpendicular to the optical axis.

The same figure (A) shows the reference state before movement, and the same figure (B) shows off-axis (image height y=±18
FIG. 4 is an explanatory diagram of a state of a light beam that forms an image on the axis (mm) and on the axis (y=o).

As shown in the figure, when the movable lens group V is decentered in the positive direction (upward), the amount of light increases at locations where the image height is positive, and the amount of light decreases significantly at locations where the image height is negative. , there is a significant difference in image plane illuminance between the upper and lower sides of the screen, resulting in uneven brightness within the screen.

This is because for a negative image height (lower side of the screen), the effective diameter of the movable lens group V deviates from the effective diameter of the fixed lens group C, which reduces the amount of off-axis light flux, and the movable lens This is because even though the light beam is focused at the same image height due to the prism effect due to the eccentricity of the group V, the upper angle of view increases and the amount of light decreases.

That is, for the image height (upper side of the screen), two lens groups v,
In addition to being almost unaffected by the effect that the effective diameters of C are shifted from each other, due to the prism effect due to eccentricity of the movable lens group V, even though the light beams are focused at the same image height, the upper angle of view is apparently reduced, so there is a surplus. This is caused by the passage of light rays.

Figures 3 and 4 show the reference state and movable lens group in Figures 2 (A) and (B), respectively, 5 m in the direction orthogonal to the optical axis.
It shows the aperture efficiency when corrected by moving m.

Further, FIGS. 5 and 6 show aberration diagrams in the reference state and during correction.

As shown in FIG. 4, the phenomenon in which the light quantity distribution increases in a part of the peripheral area of the screen does not occur if the effective diameters of the fixed lens group C and the movable lens group V are sufficiently large. however,
If this happens, the outer diameter of the lens becomes significantly large, which impairs operability, which is undesirable, so the effective diameter is generally made small.

As shown in Fig. 4, when the movable lens group V is decentered by 5 mm to correct the pre-image, the light beam that forms an image at the positive image height (upper side of the screen) has an abnormally large number of redundant rays. 6
As shown in the figure, this causes flare, which greatly reduces image quality.

On the other hand, it is possible to reduce the decrease in peripheral light intensity by narrowing down the aperture, but this method is not preferable because the lens system becomes dark.

(Problems to be Solved by the Invention) The present invention provides a method for decentering some movable lens groups of a photographic lens having a plurality of lens groups in a direction perpendicular to the optical axis to obtain predetermined optical characteristics. A movable lens group that uses a light flux limiting member to prevent the peripheral light amount from increasing in a part of the periphery of the screen and deteriorating optical performance, thereby obtaining a well-balanced light amount distribution and, moreover, obtaining a good image. The purpose of the present invention is to provide a photographic lens having the following characteristics.

(Means for Solving the Problem) It has a plurality of lens groups and a light flux limiting member, and a photographed image is obtained by moving at least one movable lens group among the plurality of lens groups in a direction orthogonal to the optical axis. When changing the optical characteristics of the lens, the amount of off-axis light flux is limited to 11 by moving the light flux limiting member in a direction perpendicular to the optical axis with respect to the movement of the movable lens group.

(Embodiment) FIG. 1 is a schematic diagram of an optical system according to an embodiment of the present invention. The figure shows a case where image blur is corrected using a movable lens group V. This figure is a cross-sectional view of the lens after the movable lens group V is moved by a predetermined amount from the reference state position to correct the image pretension.

The photographic lens of this example has a focal length of f-300 and F2.8.
It is. In the figure, C is a fixed lens group, and ■ is a movable lens group, which is moved in a direction perpendicular to the optical axis, that is, parallel decentered, to correct image pretension.

P is a light flux limiting member.

In this embodiment, an image pre-detection means (not shown) detects the pre-presence of the image, and an actuator (not shown) moves the movable lens group V by a predetermined amount in a direction perpendicular to the optical axis so as to correct the amount of pre-presence of the image at this time. , parallel and eccentric. The figure shows the case where the movable lens group V is eccentrically eccentric by 5 mm+parallel in the direction orthogonal to the optical axis.

This corrects the pre-image on the image plane by about 5 mm.

The deterioration of optical performance due to various aberrations, especially flare, as shown in Fig. 6 due to the imbalance of the light quantity distribution at the periphery of the screen as shown in Fig. 4 when the movable lens group is parallel and decentered, is to be considered. The correction is performed using a light flux limiting member P having a circular aperture as shown in FIG.

That is, as shown in FIG. 1, the light flux limiting member P is provided near or inside the movable lens group V, and by moving it in the opposite direction to the moving direction of the movable lens group, the light flux on one side is blocked. The light intensity distribution has improved as shown in the figure. 9th
The figure is a diagram of various aberrations at this time.

In this way, in this embodiment, by moving the movable lens group V,
It is characterized in that a luminous flux limiting member is used to correct the deterioration in optical performance that occurs when correcting image pretension.

In this embodiment, the light flux limiting member may be placed anywhere in the photographic lens as long as it can block part of the light flux around the screen. For example, it is possible to arrange them at positions a, b, c, d, etc. shown in FIG.

The moving direction of the light beam limiting member varies depending on the value of the refractive power of the movable lens group, but the point is that it is moved in a direction that blocks unnecessary light beams, and is not particularly limited.

For example, in this embodiment, the movable lens group has a positive refractive power, so it is moved in the opposite direction to the moving direction of the movable lens group, but when it has a negative refractive power, it is moved in the same direction as the moving direction of the movable lens group. By moving each of them, the object of the present invention can be satisfactorily achieved.

The shape of the aperture of the light flux limiting member is not limited to a circle, but may be any shape such as an ellipse or an oval depending on the purpose.

Further, the restriction of the passing state of the light beam may be configured by using an element that changes the transmittance characteristics by electrical means, such as a liquid crystal or an EC element, instead of using mechanical means having an aperture. .

The movement of the movable lens group and the light beam limiting member is not limited to the direction perpendicular to the optical axis, but is also made to move obliquely to the optical axis to correct the pre-image as well as the light intensity distribution and various aberrations across the entire screen. It's okay.

According to this, it is possible to correct the pre-image and aberrations in a better balance.

In this embodiment, it is preferable to arrange the light flux limiting member closer to the image plane than the aperture stop of the photographing lens, since various aberrations that occur when the light flux limiting member is moved can be corrected in a well-balanced manner.

In this example, the case where the movable lens group is moved in the direction orthogonal to the optical axis direction to correct the image pretension is shown, but the movable lens group can be used for various purposes such as image stabilization, shift photography, automatic tracking, etc. It goes without saying that the present invention can be similarly applied when moving to achieve the following.

(Effects of the Invention) According to the present invention, some movable lens groups of a photographing lens having a plurality of lens groups are decentered in a direction perpendicular to the optical axis,
When changing the various optical characteristics required for image stabilization and shift photography, by moving the light flux limiting member as described above, a well-balanced light intensity distribution can always be obtained and a good image quality can be obtained. As a result, a photographic lens having a movable lens group can be achieved.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of an optical system according to an embodiment of the present invention, and Figure 2 (
^), (B) is an explanatory diagram when the movable lens group is moved in a conventional photographic lens, Fig. 3 is an explanatory diagram of the light amount distribution with respect to Fig. 2 (A), and Fig. 4 is an explanatory diagram of Fig. 2 (B). ), FIG. 5 is an aberration diagram for FIG. 2(A), FIG. 6 is an aberration diagram for FIG. 2(B), and FIG. 7 is an implementation of the light flux limiting member according to the present invention. A schematic diagram of an example, FIG. 8 is an explanatory diagram of the light amount distribution with respect to FIG. 1, and FIG. 9 is an aberration diagram with respect to FIG. 1. In the figure, C is a fixed lens group, ■ is a movable lens group, P is a light flux limiting member, and y is an image height. Figure 3 → #A height - Catch of breath Figure 5 Isamu 6 Figure 7 Figure 8 → Image height Figure 9

Claims (3)

[Claims] (1) When changing the optical characteristics of a photographed image by having a plurality of lens groups and a light flux limiting member and moving at least one movable lens group among the plurality of lens groups in a direction perpendicular to the optical axis. 2. A photographic lens having a movable lens group, characterized in that an amount of off-axis light flux is limited by moving the light flux limiting member in a direction perpendicular to the optical axis with respect to movement of the movable lens group. (2) Claim 1, characterized in that the light flux limiting member is arranged closer to the image plane than the aperture of the photographing lens.
A photographic lens having a movable lens group as described in 1. (3) Photographing with a movable lens group according to claim 1, characterized in that the state of light flux passing through the light flux limiting member is performed using an element whose transmittance is electrically variable. lens.