JPH01284824A - Variable power optical system with vibration proof function - Google Patents

Abstract

PURPOSE:To correct blurring of an image when a variable power optical system is inclined and to mechanically simplify a movable lens group by providing a first group fixed while variable power is applied and a variable power group in order from an object side and moving a part of lens group in its first group substantially in the vertical direction against an optical axis. CONSTITUTION:The title system is provided with a first group I consisting of a focusing use lens group Ia which can move in the optical axis direction and a vibration proof use lens Ib which can move in the direction vertical to the optical axis, a second group II for variable power, a third group III for correcting an image face which is fluctuated by following up variable power, a fourth group IV and a fifth group V for an image formation, and a variable power group P is constituted of the second group II and the third group III. In such a state, by supplying the correction quantity of the same quantity to the lens group Ib substantially in the vertical direction to the optical axis with respect to the same inclination quantity to vibration, etc. of a variable power optical system, a vibration proof effect is obtained. In such a way, a variable power optical system which has corrected effectively blurring of an image which follows up vibration, etc., while evading a structural complication when the first group I is allowed to have both a focusing function and a vibration proof function can be attained.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a variable magnification optical system having a function of correcting blurring of a photographed image on an imaging plane due to vibration, a so-called anti-shake function, and particularly relates to a variable magnification optical system having a so-called anti-shake function. The present invention relates to a variable magnification optical system having an anti-vibration function in which a movable lens group is moved, for example, in a direction perpendicular to the optical axis to exhibit an anti-vibration effect.

(Prior Art) When attempting to photograph a moving object such as a moving car or aircraft, vibrations are transmitted to the photographing system, causing blur in the photographed image.

Conventionally, anti-vibration optical systems having a function of preventing blur in photographed images have been proposed, for example, in Japanese Patent Laid-Open No. 50-80147, Japanese Patent Publication No. 56-21133, and Japanese Patent Laid-Open No. 61-223819. There is.

In JP-A-50-80147, when a zoom lens has two afocal variable magnification systems, the angular magnification of the first variable magnification system is M3, and the angular magnification of the second variable magnification system is M2. Each variable magnification system performs magnification so that the relationship M, = 1-17M2 is established, and the second variable magnification system is spatially fixed to correct image blur and stabilize the image. There is.

In Japanese Patent Publication No. 5B-21133, the image is changed by moving the optical member at the negative part in a direction that offsets the vibrational displacement of the image caused by the vibration, in response to an output signal from a detection means that detects the vibration state of the optical device. Efforts are being made to stabilize the situation.

Japanese Patent Laid-Open No. 61-223819 discloses an imaging system in which a refractive variable apex angle prism is disposed closest to the subject, and an image is captured by changing the apex angle of the refractive variable apex prism in response to vibrations of the imaging system. The image is stabilized by deflecting it.

In addition, Special Publication No. 56-34847, Special Publication No. 57-
7414, etc., an optical member that is spatially fixed against vibration is arranged in a part of the photographing system, and the photographed image is deflected and formed by utilizing the prism effect that occurs when the optical member is photographed. A still image is obtained on the surface.

In addition, it uses an acceleration sensor to detect vibrations in the shooting system,
There is also a method of obtaining a still image by vibrating a part of the lens group of the photographing system in a direction perpendicular to the optical axis in accordance with the signal obtained at this time.

In general, models that obtain still images by vibrating some lens groups in the shooting system are designed to simplify the relationship between the amount of image blur correction and the amount of movement of the movable lens, and to There is a need for an imaging system with a simple configuration that reduces calculation time.

(Problems to be Solved by the Invention) The present invention solves the problem by simplifying the mechanism of the movable lens group when correcting image blur by moving some lens groups of the variable magnification optical system in a direction perpendicular to the optical axis. The object of the present invention is to provide a variable magnification optical system with a simple structure and an anti-vibration function.

(Means for solving the problem) A variable power optical system having a first group that is fixed during variable power and a variable power group in order from the object side, the first group being a focusing lens group 1a.
and lens group 1b, and the lens group 1b has two lens groups.
By moving at least some of the lens groups in b in a direction substantially perpendicular to the optical axis, blurring of the image on the imaging plane when the variable magnification optical system is tilted is corrected. .

(Embodiment) FIG. 1 is a schematic diagram of an optical system according to an embodiment of the present invention. In the figure, the lens has a first lens group that is fixed during zooming, a focusing lens group Ia that is movable in the optical axis direction, and a vibration isolation lens group Ib that is movable in the direction perpendicular to the optical axis, which will be described later. ing. ■ is the second group for zooming, ■ is the third group for correcting the image plane that changes with zooming, and the second group ■ and the third group m constitute the variable magnification group P. For example, as shown in the arrow The magnification is changed from the wide-angle end to the telephoto end by moving the lens in a similar manner. (2) is the fourth group, and the light beam emitted from the third group is made almost afocal. ■ is the fifth group for imaging, sp
is a fixed aperture.

In general, in a variable magnification optical system, when the variable magnification optical system is tilted by a certain amount (angle θ), the amount of blurring ΔY of the image from a predetermined position on the imaging plane is as follows, where f is the focal length, ΔY = f - tan θ . Therefore, in order to correct the amount of image deflection at this time using a lens group behind the variable magnification group, it is necessary to control the amount of correction in accordance with the focal length f.

On the other hand, in a variable magnification optical system as shown in Fig. 1, the sensitivity of the first group, which is located closer to the object side than the variable magnification group P and has a fixed focusing function during variable magnification, with respect to parallel eccentricity is determined by the focal length. It has the property of being proportional to.

Therefore, in this embodiment, taking advantage of this property, the first group is divided into two lens groups, lens group Ia and lens group Ib, so that the lens group I
The anti-vibration effect is obtained by applying the same amount of correction to b in a direction substantially perpendicular to the optical axis.

Furthermore, a focusing function is provided by moving the lens group Ia on the optical axis. This allows us to create a variable magnification optical system that effectively corrects image blur caused by shooting, while avoiding the structural complexity that would arise when the first lens group has both a focusing function and an image stabilization function. Achieved.

Next, a numerical example will be shown when image stabilization is performed using lens group Ib in this embodiment. Now, let β1 be the imaging magnification of the i-th group, fI be the focal length of the i-th group, and f be the focal length of the entire system.
The amount of movement of the image in the direction perpendicular to the optical axis relative to the unit movement in the direction perpendicular to the optical axis of the i-th group, that is, the sensitivity of parallel eccentricity S□ is the product of the imaging magnification from the (i+1)th group to the final group. β, +
1~. Then, SP,=(1-βI)・β,. , ν. On the other hand, f=f, ·β2~, and since β1=0 for an object at infinite distance, 5P2=(1−β2)·β3~ and 2β3~k −β2~.

On the other hand, since the image blur amount ΔY is ΔY=f−tanθ, the amount of movement δ of lens group Ib in the first group in the direction perpendicular to the optical axis to correct the amount of blur in this image is δ=−ΔY /S P2.

Therefore, in this embodiment, the focal length of the zoom position of the variable magnification optical system is 1.
! Regardless of the value of 1llf, image blur can be corrected by moving the lens group Ib by δ in the direction perpendicular to the optical axis.

In this example, in the region where the tilt angle θ is small, janθ
Since the cape is θ, in simple terms, image blur can be corrected even if lens group Ib is partially rotated with the center β2 at a position 1/(-1) of the focal point of lens group Ib in the first group. can do. At this time, the lens tilts slightly, but the image point does not shift.

In this embodiment, even if some lens groups Ibb of the lens groups Ib in the first group are moved in the direction perpendicular to the optical axis, image blur can be corrected in the same manner as described in the above. In this case, the amount of correction, the fulcrum of rotation, etc. may be appropriately set depending on the sensitivity of the lens group Ibb.

The variable power optical system according to this embodiment can be applied to any zoom type as long as it has a variable power system after the first group.

In this embodiment, when focusing is performed using the lens group Ia in the first group, the imaging magnification β1a of the lens group a for an object at infinity is set so that 1βlal≠1, and 1βla
When l>1, move toward the image plane with respect to the close object,
Further, when 1βlal<1, the object is moved toward the object at a short distance.

(Effects of the Invention) According to the present invention, in a variable power optical system having a first group having a focusing function and a variable power group, at least a portion of the lens group Ib on the image plane side in the first group By moving a lightweight lens group in a direction substantially perpendicular to the optical axis, image blur can be corrected with the same amount of correction for the same amount of tilt due to vibration, etc., regardless of the focal length of the variable magnification optical system. It is possible to achieve a variable magnification optical system having an anti-vibration function that can perform quick and effective correction while avoiding complication of the configuration of one group of lens barrels.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of an optical system according to an embodiment of the present invention. In the figure, engineering is the first group, P is the variable magnification group, ■ is the second group for variable magnification,
(2) is the third group for image plane fluctuation correction, (2) is the fourth group, (2) is the fifth group, sp is the diaphragm, Ia is the lens group for focusing, and Ib is the lens group for correcting image blur. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] This is a variable magnification optical system having, in order from the object side, a first group that is fixed during zooming and a variable magnification group, the first group being a focusing lens group 1a.
and lens group 1b, and the lens group 1b has two lens groups.
By moving at least some of the lens groups in b in a direction substantially perpendicular to the optical axis, blurring of the image on the imaging plane when the variable magnification optical system is tilted is corrected. A variable magnification optical system with anti-vibration function.