JP2511822B2 - Photographic lens with movable lens group - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographic lens having a movable lens group, and particularly to moving the movable lens group in a direction orthogonal to an optical axis to change optical characteristics of a captured image. The present invention relates to a photographic lens having a movable lens group that maintains a well-balanced light amount distribution around the screen when it is turned on.

(Prior Art) Conventionally, various methods have been used to obtain a predetermined optical characteristic by moving a part of the movable lens group of the taking lens in a direction orthogonal to the optical axis. For example, (a) JP-A-62-44
In Japanese Patent No. 707, blurring of a captured image that occurs when capturing an image from a moving object such as a car or an airplane in progress is corrected by moving the movable lens group in a direction orthogonal to the optical axis.

(B) In many photographic cameras and video cameras,
In the case of shift shooting for shooting a building without distortion, a part of the movable lens group of the shooting lens is decentered.

(C) In automatic tracking photography such as panning photography, the moving speed of the subject image is detected by the image sensor, and a part of the movable lens group is eccentrically driven so that the subject does not move on the film surface. As a result, the drive response is improved compared to when the entire optical system is shaken.

(D) When making fine adjustments to the super-telephoto lens, etc., to improve the operability of framing, if the entire lens system is rotated, the screen will move greatly with a small movement. It is performed by moving in a direction orthogonal to the optical axis. This aims to improve the operability of framing.

FIGS. 2A and 2B are schematic diagrams of an optical system of one embodiment in which the movable lens group V is moved in a direction orthogonal to the optical axis to correct, for example, blurring of pixels.

The figure (A) shows the reference state before the movement, and the figure (B) shows the off-axis (image height y = ± 18 m when the movable lens group V is moved by 7 mm).
It is explanatory drawing of the light beam state which image-forms on m) and an axis (y = 0).

As shown in the figure, the movable lens group V is moved forward (upward).
When eccentric to, the amount of light increases at the place where the image height is positive,
When the image height is negative, the amount of light is significantly reduced, and there is a significant difference in image plane illuminance between the upper side and the lower side 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, so that the light amount of the off-axis light beam decreases. Group V
This is because even if the luminous flux is imaged at the same image height due to the prism action due to the eccentricity, the apparent 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,
The effective diameter of C is hardly affected by the mutual displacement, and in addition, even if the luminous flux is imaged at the same image height due to the prism action due to the eccentricity of the movable lens group V, the apparent angle of view is reduced and the surplus light rays are generated. Occurs because of the passage of.

FIGS. 3 and 4 show the reference state in FIGS. 2A and 2B and the aperture efficiency when the movable lens group is moved by 5 mm in the direction orthogonal to the optical axis and corrected. Further, FIGS. 5 and 6 show aberration diagrams at the time of correction and the reference state.

As shown in FIG. 4, the phenomenon in which the light amount distribution increases in a part of the peripheral portion 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 is the case, the outer diameter of the lens becomes extremely large and the operability deteriorates, which is not preferable, 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 blurring of the image, the light beam formed at the positive image height (upper side of the screen) has an excessive amount of extra light rays, and the light rays are 6
As shown in the figure, flare is caused, which causes a significant deterioration in image quality.

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

(Problems to be Solved by the Invention) In the present invention, when a part of a movable lens group of a photographing lens having a plurality of lens groups is decentered in a direction orthogonal to an optical axis to obtain predetermined optical characteristics, decentering is performed. A movable lens group capable of obtaining a well-balanced light amount distribution by preventing a decrease in optical performance due to an increase in peripheral light amount at a part of the periphery of the screen due to the use of a light flux limiting member, and further obtaining a good image. An object of the present invention is to provide a photographic lens having

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

FIG. 1 is a schematic view of an optical system according to an embodiment of the present invention.
In the figure, the case where the image blur is corrected using the movable lens group V is shown. This figure is a lens cross-sectional view after moving the movable lens group V from the position in the reference state by a predetermined amount to correct the blurring of the image.

The taking lens of this embodiment has a focal length f = 300 and F2.8. In the figure, C is a fixed lens group, and V is a movable lens group which is moved in a direction orthogonal to the optical axis, that is, parallel eccentricity, to correct image blur. P is a light flux limiting member.

In this embodiment, image blur detection means (not shown) detects image blur, and the movable lens group V is moved in a direction perpendicular to the optical axis by a predetermined amount by an actuator (not shown) so as to correct the amount of image blur at this time. , Parallel eccentricity. This figure shows a case where the movable lens group V is decentered by 5 mm in the direction orthogonal to the optical axis. As a result, the blurring of the image is about 5 mm on the image plane.
Correcting.

Then, when the movable lens group is decentered in parallel, the sixth due to the imbalance of the light amount distribution in the peripheral portion of the screen as shown in FIG.
Deterioration of optical performance due to various aberrations as shown in the figure, particularly due to flare, is corrected by 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 in the vicinity of or inside the movable lens group V, and is moved in the direction opposite to the moving direction of the movable lens group to block the light flux on one side. The light quantity distribution is improved as shown in. FIG. 9 is a diagram of various aberrations at this time.

As described above, the present embodiment is characterized in that the movable lens group V is moved to correct the deterioration of the optical performance that occurs when the image blur is corrected by using the light flux limiting member.

In this embodiment, the light flux limiting member may be arranged anywhere in the photographing lens as long as it can shield a part of the light flux around the screen. For example, they can be arranged at the positions a, b, c, d, etc. shown in FIG.

The moving direction of the light flux limiting member differs depending on the value of the refractive power of the movable lens group, but the point is that the light flux limiting member may be moved in the direction in which unnecessary light is blocked, and is not particularly limited.

For example, in this embodiment, since the movable lens group has a positive refractive power, it is moved in the direction opposite to the moving direction of the movable lens group. However, when the refractive power is negative, it is moved in the same direction as the moving direction of the movable lens group. If each is moved, the object of the present invention can be achieved well.

The aperture shape of the light flux limiting member is not limited to a circular shape, but may be an elliptical shape, an oval shape, or any other shape depending on the purpose.

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

The movement of the movable lens group and the light flux limiting member is not limited to the direction orthogonal to the optical axis, but may be moved in an oblique direction with respect to the optical axis so as to correct the image blur and the light amount distribution and various aberrations of the entire screen. May be.

According to this, the blurring and the aberration of the image can be corrected in a better balance.

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

In this embodiment, the case where the movable lens group is moved in the direction orthogonal to the optical axis direction to correct the blurring of the image is shown. However, the movable lens group is used for each of the above-mentioned purposes such as image stabilization, shift photographing, and automatic tracking. It is needless to say that the present invention can be similarly applied to the case of moving in order to achieve the above.

(Effect of the Invention) According to the present invention, a part of the movable lens group of the photographing lens having a plurality of lens groups is decentered in the direction orthogonal to the optical axis, and is required at the time of image stabilization or shift photographing. When changing the optical characteristics, by moving the light flux limiting member as described above, a well-balanced light amount distribution can be obtained at all times.
Moreover, it is possible to achieve a photographic lens having a movable lens group capable of obtaining a good image.

[Brief description of drawings]

FIG. 1 is a schematic view of an optical system according to an embodiment of the present invention, FIGS. 2A and 2B are explanatory views when a movable lens group is moved in a conventional taking lens, and FIG. 2 (A) is an explanatory diagram of the light amount distribution, FIG. 4 is an explanatory diagram of the light amount distribution for FIG. 2 (B), FIG. 5 is an aberration diagram for FIG. 2 (A), and FIG. 6 is FIG. FIG. 7 is an aberration diagram for (B), FIG. 7 is a schematic diagram of an embodiment of a light flux limiting member according to the present invention, FIG. 8 is an explanatory diagram of a light amount distribution for FIG. 1, and FIG. 9 is an aberration diagram for FIG. Is. In the figure, C is a fixed lens group, V is a movable lens group, P is a light flux limiting member, and y is the image height.

Claims (3)

(57) [Claims] 1. A plurality of lens groups and a light flux limiting member,
When changing the optical characteristics of the captured image by moving at least one movable lens group of the plurality of lens groups in a direction orthogonal to the optical axis, the light flux limiting member is moved along the optical axis with respect to the movement of the movable lens group. A photographing lens having a movable lens group, wherein the amount of off-axis light flux is limited by moving in a direction orthogonal to the. 2. A photographic lens having a movable lens group according to claim 1, wherein the light flux limiting member is arranged closer to the image plane side than an aperture of the photographic lens. 3. The movable lens group according to claim 1, wherein the light flux passing state by the light flux limiting member is made by utilizing an element for electrically varying the transmittance. Taken lens.