JPS63201622A - Image stabilization optical system and attachment - Google Patents

Abstract

PURPOSE:To vary the focal length of a main lens and to prevent vibration by making part of an afocal system attachment lens eccentric in parallel. CONSTITUTION:The specific part of an afocal optical part A which constitutes an optical system with a main lens system 1 or the afocal attachment mounted on part of the main lens system 1 is allowed to move freely at right angles to the optical axis of the optical system, and the remaining part is fixed; and the movable part is made eccentric in parallel according to a force which is applied from outside. Consequently, the constitution is reduced in size, the load on a driving mechanism is small, and deterioration in picture quality, specially, chromatic aberration is reducible.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field> The present invention relates to an optical system and an attachment having a mechanism for deflecting an image, and is particularly suitable for use in an anti-vibration device.

<Prior Art> There has been an extremely high demand for image stabilization, that is, optical image stabilization. Shaking of the photographic screen is usually caused when the camera is installed in a car, ship, or helicopter, or is moved hand-held when photographing sports events or news reporting.

Sports broadcasts or news programs are often shot with a video camera or cine camera, but even with a still camera, when hand-held shooting with a long focal length lens attached, the image is likely to blur, especially This is difficult to avoid if the exposure time is long.

For this reason, various anti-vibration optical systems have been proposed so far.

One of the known optical image stabilization devices employs a method in which an optical wedge is provided in the imaging system, and the deviation of the optical path due to vibration is corrected by changing the angle of the optical wedge and using its prism effect. An optical wedge is formed by tilting one lens of a doublet lens, in which the uneven surfaces of a plano-convex lens and a plano-concave lens face each other, or by tilting one surface of a liquid-filled bellows with respect to the other surface. Even if we search for lens materials and liquids with a high ratio, there are limits, and we can only correct about half of the required angle of inclination. Therefore, it has been proposed to provide a plurality of optical wedges or to place a wide converter in front to utilize the combined effect, but the former requires a complicated drive mechanism, and the latter tends to increase the size.

Also, in any case, a prism has been introduced, so
Even if measures are taken to correct chromatic aberration, colors tend to appear on the image.

When tilting one side of the doublet lens mentioned above, the lens must be supported so that it can swing vertically and horizontally around the spherical center of the lens surface, and it must also be connected to a gyroscope installed at this position to move it. It has the drawback of requiring considerable precision in order to accurately maintain the center and realize smooth operation, which places a considerable burden on the drive mechanism.

<Problems to be Solved by the Invention> It is an object of the present invention to solve the above-mentioned difficulties, to be relatively compact, to place less burden on the drive mechanism, and to reduce deterioration in image quality, particularly chromatic aberration.

In order to achieve this purpose, the afocal optical part that constitutes the optical system together with the main lens system, or a predetermined part of the afocal attachment that is attached to and detached from a part of the main lens system, can be freely moved in the direction perpendicular to the optical axis of the optical system. The remaining part is fixed and the movable part is parallel and eccentric in response to external forces.

<Embodiment> Hereinafter, the basic configuration of an embodiment of the present invention will be explained using FIGS. 1 to 3. FIG. 1 shows a normal state, that is, a state in which no external force is applied to the optical system. Figures 2 and 3 show a state in which an external force is applied to the optical system, causing it to rotate upward, for example. Figure 2 shows when the anti-vibration function is not operating, and Figure 3 shows when it is operating. It is.

1 in the figure is a main lens such as an imaging lens, and although it is depicted as a block here, it actually consists of multiple lenses, and may be a single focus lens or a zoom lens. . 2 is the optical axis of the main lens l. 3 indicates a screen, on which a photosensitive film and an image sensor are arranged. 4 and 5 degrees are light rays, respectively, which are assumed to be from a point light source at an infinite distance, and form a point image 6 on the screen 3. 7 is a positive lens portion, and 8 is a negative lens portion, which are shown in the drawing using a thin-wall notation. The positive lens section 7 and the negative lens section 8 constitute an afocal optical system A, and may be provided as a detachable attachment to the main lens l, or may be provided in the same lens barrel (not shown) as the main lens l. Also good. Each lens section is composed of one or more lenses depending on the desired image quality, but as will be described later, it is desirable that the movable lens section is composed of at least one positive lens and one negative lens. In this example, the negative lens section 8 is movable perpendicularly to the optical axis 2.

In addition, here, the afocal optical system A is a wide type, but it may be a tele type, and if the main lens l is a telephoto type, it is a tele type. If you are looking for a wide-angle lens, it is natural to use the wide type, but you can also select the opposite option if necessary.

The negative lens section 8 is supported by a support member (not shown) so as to be movable in a plane perpendicular to the optical axis 2, and is driven by an actuator 9. Various types of actuator 9 can be used, such as a solenoid, a meter, and a stack of piezo elements. 10 is a deflection detector which includes a gyroscope, an accelerometer, an angular accelerometer, a speedometer, etc. If you use a gyroscope, you can get the inclination angle, and if you use an accelerometer, you can integrate the output twice to get the amount of deviation at the position where the accelerometer is attached, so based on this, you can calculate the amount of compensation movement of the negative lens section 8. It can be calculated.

In FIG. 1, rays 4 and 5 pass through a positive lens section 7 and a negative lens section 8, and are imaged onto a screen 3 by a main lens l. The dotted line 6 is at the center of the screen 3. Next, when an external force is applied to the optical system and the optical system is rotated, for example, around a node, the image point 6 is displaced from the center of the screen 3 as shown in FIG. In other words, the object image moves on the screen 3, and the object image vibrates as external forces are applied repeatedly.

As shown in FIG. 3, if the bias detector lO and the actuator 9 are operating, the bias detector lO detects the compensation movement amount and drives the actuator 9. Since the actuator 9 moves the negative lens section 8 in a direction perpendicular to the optical axis 2, the image point 6
remains centered on the screen. The optical correction effect will be described later.

FIG. 4 schematically shows the drive mechanism of the negative lens section 8. In short, a configuration is required in which the negative lens portion 8 can be moved independently in two directions, vertical and horizontal, and simultaneously in two directions in order to move in an oblique direction.

Note that for special applications or simplified devices, movement in one direction may be sufficient. In the figure, 11 is an outer lens barrel, and 12 is an inner lens barrel. The first actuator 9a and the first slide bearing 13 are provided at opposing positions of the outer lens barrel 11, and support the inner lens barrel 12 with a shaft and maintain it in a neutral position with a spring. 12 can be moved to a desired position. The outer lens barrel 11 is the second
The negative lens portion 8 is similarly supported by the actuator 9a and the second slide bearing 14, and can move the negative lens portion 8 to a desired position.

In this mechanism, the vertical movement by the first actuator 9a and the horizontal movement by the second actuator can be performed independently or in a superimposed manner.

FIGS. 5 and 6 are diagrams illustrating how light rays are tilted when a part of the afocal optical system is decentered in parallel in a direction perpendicular to its optical axis.

Now, let us assume that the power of the positive lens section 7 is φ1, and the power of the negative lens section 8 is φ2, and when the negative lens section 8 is parallel decentered by the amount of compensation, the emitted light ray will be tilted by an angle of -Dφ2. This will be explained using paraxial tracking. Let the incident angle of the upper ray 4 entering the negative lens section 8 be αu2, the height hu2 from the optical axis at that time, and the exit angle α'u2, and similarly for the lower ray 5 αd2 + hd2 +
Defining α/a2, in the case of Figure 5, the upper line 4; a u2+hu2*φ2 =0”
”” (1) Underline 5; αd2+hd2・φ2
=0... (2) Also, in the case of Figure 6, the upper line 4; (!' u2=αu2+(hu2-D)φ
2=αu 2 +hu 2・φ2−D・φ2・・・・
・・・・・・(3) Underline 5; α′d2=αd 2+ (
hd 2-D) φ2=αd2+hd2・φ2-D・φ2
・・・・・・・・・(4) Substitute l into equation (3) and get (4
) By substituting (2) into the equation, a'u2=-Dφ2. a
' d2 = -D-φ2 That is, the emission angles of the upper line and the lower line are both tilted by -Dφ2, so this property can be utilized to compensate for image movement.

According to this method, the light beam corresponds to the parallel eccentricity measurement and -Dφ2
Since it is tilted, by setting φ2 to a large value, the vibration isolation effect can be increased with a small movement. Furthermore, unlike conventional optical wedges, it is not limited by the refractive index of the material, so the sensitivity (response of image movement to lens movement) can be set relatively freely.

Also, in the above explanation, the rear convergent lens part of the afocal optical system, which consists of a diverging lens part and a converging lens part, is parallel decentered, but if any part of the lens in the afocal optical system is parallel decentered, the upper line This is extremely convenient since it can be said from similar paraxial tracing that the angle of inclination of the underline and the underline will be the same.

7 to 9 show modifications of FIG. 1, respectively. Fig. 7 shows an example in which the afocal optical system is arranged on the image side of the main lens l, and Fig. 8 shows an example in which the afocal optical system is arranged in a positive lens section 8a, a negative lens section 7', and a positive lens section 8b. In this example, the actuator 9 is used to make the two positive lens parts 8a and 8b parallel and decentered.

FIG. 9 shows an example in which an afocal optical system consisting of three parts is arranged on the image side of the main lens l.

Next, FIG. 10 shows an example in which each lens portion is made thicker.

Numerical specifications will be described later. The main lens of l is a telephoto lens, and using the data of Example 1 of Japanese Patent Publication No. 60-328°47 converted to a focal length of 300 mm, the optical system that combines afocal optical system A and this telephoto lens is used. The combined focal length is 352.94mm, F number 1: 5.6. The angle of view 2W=7°.

The afocal optical system of this example is a teletype, and consists of four lenses in two groups: a positive lens section AI and a negative lens section A2, with the negative lens section A2 being parallel and decentered.

It is preferable that the configuration described above satisfies the following conditions from a design standpoint.

-3≦Fp/Fn≦-1 However, Fp is the focal length of the positive lens portion, and Fn is the focal length of the negative lens portion. If the lower limit value is exceeded, the amount of movement of the image relative to the unit movement amount of the movable part, that is, the sensitivity value deteriorates, and if the upper limit value is exceeded, it becomes difficult to improve the image performance.

On the other hand, although it is much smaller than a conventional device using an optical wedge, chromatic aberration worsens because a lens whose optical axis is shifted from other lenses is introduced. However, the chromatic aberration of the movable lens section itself can be suppressed to a minimum, thereby improving the aberration.

When the movable lens portion has a negative refractive power α, the average Abbe number of the positive lenses constituting the lens portion is νp1, and the average Abbe number of the negative lenses is 7n, satisfying vp≦40°dn≧45.

Conversely, when the movable lens part has a positive refractive power, the average Atsube number of the positive lenses constituting the lens part is νp, and the average Atsube number of the negative lenses is 7n, and the following conditions are satisfied: yp≧45° dn≦40 .

If these conditions are not satisfied, chromatic aberration, especially chromatic aberration of magnification, may become noticeable when the lens portion is decentered.

FIG. 11 shows the reference performance due to longitudinal aberration of a numerical example of the present invention. Also, the aberration coefficient values of each lens group at this time are also given.

FIG. 12 shows the performance in the above-mentioned standard state (a state in which there is no image blur due to camera shake, etc.) in terms of lateral aberration. Image height Y=15 from above. O, -15.

FIG. 13 shows the performance in a state where, when image blur occurs by l m m, the negative eccentric block A2 is parallel and decentered by 0.6 mm, the image is shifted by 1 mm, and the image blur is canceled.

As can be seen by comparing the performance with the performance shown in FIG. 12, it can be said that there is almost no deterioration of aberrations due to parallel eccentricity.

This satisfies the following conditions: -4≦AO2≦0 and -1≦BO2≦3. A used here. 2゜8
02 is the characteristic coefficient A for determining the shape R of the A2 block in the thin optical system. , Bo (see Yoshiya Matsui: Lens Design Method). A of A2 block. 2°BQZ When this condition is not satisfied, aberrations are greatly worsened even when A2 is parallel decentered and image blur is corrected. In particular, eccentric comatic aberration, eccentric astigmatism, eccentric curvature of field, and eccentric distortion aberration are newly generated.

Also, the radius of curvature and radius R1 (rs) of the first surface in the A2 block
When the radius of curvature of the final surface is Rk (r,), it is convenient for setting if the following conditions are satisfied.

-1≦(R,+Rk)/(R+Rk)≦1.5If the lower limit of this conditional expression is exceeded, spherical aberration will be overcorrected in the standard state, and if the movable lens group A2 is parallel decentered, eccentric coma aberration will occur. growing.

Furthermore, when the upper limit of the above conditional expression is exceeded, coma aberration begins to occur in the standard state, and when A2 is parallel decentered, eccentric coma aberration and eccentric astigmatism occur.

<Example> f = 352.94 Fno, = 1:5.6 2w =
7°RD ND VD When the entire system is normalized to 1, the inclination angle of the light beam is 2.08D when φ2=-2.08.

Fp/Fn=-1,2 LI A=52.3 A0=1.87B=35.3
80=0.39 1, 10Rk)/(R, -Rk)=o, sta Sharing value of the difference coefficient of each lens group L TSAC1lASFrDS ^11-40.030481-0.0056830.5
368090.3000961.51120531.0
72464-1.148775^25-8-0.030
9660.003577-0.084701-0.42
9071-1.469197-1.0772930.5
20091B 9-170.0005960.01X1
4530.4026070.2641870.1?11
6j -0,080139-5,807461L is lateral chromatic aberration, T is axial chromatic aberration, SA is spherical aberration, C
M is comatic aberration, AS is astigmatism, PT is Petzval sum, and DS is distortion coefficient.

In addition to using an afocal optical system as an attachment, the present invention can also be applied to systems where the optical system itself is afocal.

For example, telescopes, binoculars, and finders. In addition, although the above case was described as a vibration isolator, it can also be used to scan the field of view.

<Effects> Since the present invention performs vibration isolation by paralleling and decentering a part of the afocal attachment lens, it is possible to change the focal length of the main lens, which could not be achieved with a vibration isolation system using a variable apex angle prism using tilt decentering. It is possible to change the magnification, and it can be used as an attachment to make it telephoto or wide-angle, and it also has vibration isolation.

Also, the inclination angle of the light beam when the parallel eccentric block is parallel eccentric is expressed as -Dφ2, which becomes the parameter of φ2, and φ
The sensitivity can be increased by setting the value of 2 to be thicker (setting).And by making the parallel eccentric lens group with a large sensitivity, the parallel eccentric lens group (correction lens group) can be simply moved vertically or horizontally. Since image blur can be corrected by simply shifting a small amount, the actuator can be made compact without requiring a complicated one.Also, the small amount of shift of the parallel decentered lens group is sufficient even for high frequency and large amplitude vibrations. It can be corrected to

This fast response speed allows signals to be fed back from the sensor to the actuator many times, making it possible to correct vibrations in real time.

[Brief explanation of the drawing]

FIG. 1 is an optical layout diagram showing an embodiment of the present invention, FIGS. 2 and 3 are diagrams showing the state when an external force is applied, and FIG.
The figure is a front view of the drive mechanism. 5 and 6 are explanatory diagrams of optical effects, and FIGS. 7, 8, and 9 are optical layout diagrams showing modified examples, respectively. FIG. 10 is a sectional view of the lens of the example. Figure 11,
FIG. 12 and FIG. 13 are aberration diagrams, respectively. In the figure, 1 is a main lens, A is an afocal optical system, 7 is a negative lens section, 8 is a positive lens section, and 9 is an actuator.

Claims (8)

[Claims] (1) Equipped with a main lens and an afocal optical section that constitutes an optical system together with the main lens, a predetermined part of the afocal optical section is movable in a direction perpendicular to the optical axis of the optical system, and the remaining part is integrated with the main lens. An image stabilizing optical system characterized in that a movable part is parallel and decentered in response to an external force applied to the optical system. (2) The image stabilizing optical system according to claim 1, wherein the afocal optical section is composed of a portion with positive refractive power and a portion with negative refractive power, one of which is movable and the other fixed. . (3) The image stabilizing optical system according to claim 1 or 2, wherein the movable portion includes a positive lens and a negative lens. (4) an afocal optical section that is attached to and detached from the object side or image side of the main lens, a predetermined portion of the afocal optical section being movable in a direction perpendicular to the optical axis, and the remaining portion being fixed;
An attachment characterized by making a movable part parallel and eccentric in response to applied force from the outside world. (5) The attachment according to claim 4, wherein the afocal optical section is composed of a portion with positive refractive power and a portion with negative refractive power, one of which is movable and the other fixed. (6) When the focal length of the positive refractive power portion is Fp and the focal length of the negative refractive power portion is Fn, −3≦Fp/
The attachment according to claim 5, which satisfies Fn≦-1. (7) The positive refractive power part is movable and has a positive lens and a negative lens, and the average Atsube number of the positive lens is νp,
When the average Atsube number of a negative lens is @ν@n, @ν@
The attachment according to claim 5, which satisfies p≧45 and @v@n≦40. (8) The part with negative refractive power is movable and has a positive lens and a negative lens, and the average Atsube number of the positive lens is @ν@
p, when the average Atsube number of the negative lens is @ν@n, @ν
The attachment according to claim 5, which satisfies @p≦40 and @ν@n≧45.