JPH08201694A - Image blurring correcting variable power optical system - Google Patents

Abstract

PURPOSE: To decrease the effective diameter of a fixed lens by making a front lens composing an afocal front group a movable lens and a lens arranged behind the fixed lens in an image blurring correcting variable power optical system. CONSTITUTION: A first group A1 and a succeeding variable power group A2 are arranged in order from the object side in an optical system A and the first group A1 is composed of a front group A1F of an afocal system and a rear group A1R having a positive refractive power. The front group A1F is composed of a movable group A1Fa and a fixed group A1Fb arranged behind and when the optical system A is inclined, the movable group A1Fa is moved in the direction orthogonal to the optical axis L-L by means of a lens driving part LD. By making the movable group A1Fa a positive lens and the fixed group A1Fb a negative lens, the interval between the fixed group A1Fb and the rear group A1R is shortened. By making the movable group A1Fa a negative lens and the fixed group A1Fb a positive lens, the focal distance of the system is shortened and the viewing angle is expanded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image blur correcting variable magnification optical system for performing image blur correction by moving a movable group constituting an afocal system in a direction orthogonal to the optical axis of the entire system. It is possible to reduce the effective diameter of the lens relating to the fixed group by making the front lens group constituting the afocal system a movable group and the lens group arranged behind it a fixed group. It is intended to provide a new image blur correction variable magnification optical system as described above.
The optical system of a portable video camera or the like can perform suitable image blur correction.

[0002]

2. Description of the Related Art Since a small portable video camera or the like is light in weight, camera shake is likely to occur at the time of shooting and, for example, when an image taken by zooming up is reproduced, image blurring occurs.

Therefore, various methods have been proposed for camera shake correction. For example, the movement of the main body of the apparatus is detected by a camera shake sensor and the lens group forming a part of the photographing system is moved to eliminate image blur. Such a lens system is known.

For example, an optical system a shown in FIG. 8 has an optical axis L-
It is composed of five lens groups arranged along L, and the afocal part A1F on the most object side which constitutes the first group G1 is arranged such that a movable positive lens is arranged behind the negative lens. There is. The rear lens group A1R that constitutes the first lens group G1 is composed of three lenses, the second lens group G2 has three lenses, the third lens group G3 has one lens, and the fourth lens group G4 has two lenses.
The fifth group G5 is composed of three filters.

An aperture stop (indicated by "STOP" in the figure) is arranged in front of the lens of the third lens group G3.
The image surface (denoted as "SF" in the drawing) is located behind the fifth lens group G5 by a predetermined distance.

In this example, a biconcave lens and a biconvex lens are used as the two lenses forming the afocal portion A1F, the biconcave lens b1 located on the front side is a fixed lens, and the biconvex lens b2 located on the rear side is a movable lens. The biconvex lens b2 is moved by a moving unit (not shown) in a direction perpendicular to the optical axis L-L, that is, in the vertical and / or horizontal direction.

The ray c is a biconvex lens b2 with respect to light incident on the lens system a at an angle θ with respect to the optical axis L-L.
Is moved in the direction shown by the arrow D, the optical axis L-
The optical path when the image blur correction is performed along L is shown.

[0008]

By the way, in the optical system using the rear lens b2 of the afocal portion A1F as the movable lens as described above, the size of the movable lens determines the outer diameter of the entire system. However, since it is difficult to reduce the effective diameter of the movable lens, there is a problem that this hinders downsizing of the device.

The effective diameter of the second (rear) lens b2 in the afocal portion A1F is obtained by a ray tracing process in consideration of the image height, the ray position on the diaphragm surface, and the like.

In other words, in order to receive light without a shortage of the amount of light on the image plane, the condition that the light beam reaches the effective area of the light receiver must be satisfied. For example, 1/4
In inch CCD type area image sensor, image height h =
2.25 mm is required.

Further, in order for the light rays to reach the image plane even when the diaphragm is fully closed, the light rays must pass through the center of the diaphragm surface.

The ray d shown in FIG. 8 is obtained by performing ray tracing on the front side (object side) so as to satisfy the above conditions, and Snell's law is applied to each lens surface using optical design software. Calculated by applying As a result, the intersection point A between the ray d and the object-side surface of the lens b2 (referred to as "S3") is determined, and the lens b2.
The effective diameter is defined by the height h of the intersection A obtained when the lens is moved in the direction orthogonal to the optical axis L-L (double the sum of the height h and the movement amount of the lens b2). Is the effective diameter.)

FIG. 9 is a schematic diagram for explaining the effective diameter of the movable lens when the rear lens b2 in the afocal portion A1F is a movable lens.

FIG. 9A shows light rays f1 and f2 when the center of the lens b2 arranged in front of the taking lens system e is located exactly on the optical axis, and FIG. 9B shows , B2 when the lens b2 moves in the direction orthogonal to the optical axis L-L as shown by the arrow B. As is clear from the comparison between the two, the light ray g is greater than the light ray f2.
2 passes through the position closer to the peripheral edge of the lens b2,
There is a tendency that the effective diameter becomes large. That is, when image blur correction is performed by moving the lens b2 on the rear side, as the correction amount (that is, the movement amount of the lens b2) increases, light does not come off from the peripheral edge of the lens b2. Therefore, the effective diameter must be increased.

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a first group that is immovable in the optical axis direction and a variable power group that follows the first group on the object side. In the image blur correction variable magnification optical system arranged in this order from
The group consists of a front group of afocal system and a rear group having positive refractive power, and the front group consists of a movable group and a fixed group arranged behind it. The lens moving means moves the movable group in a direction orthogonal to the optical axis.

[0016]

According to the present invention, the front lens group in the front group of the afocal system is the movable group, and the fixed group is arranged behind the movable lens group. Since it becomes difficult for light to escape from the portion, the effective diameter of the lens relating to the fixed group can be reduced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The image blur correction variable magnification optical system of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows the basic configuration of the image blur correction variable magnification optical system of the present invention.
The axis indicated by "-L" indicates the optical axis of the entire system.

The optical system A comprises a first group A1 in order from the object side,
It has a configuration of a variable power optical system in which a variable power group A2 is arranged.

The first lens group A1 comprises a front lens group A1F (hereinafter referred to as "afocal portion") of an afocal system and a rear lens group A1R having a positive refractive power, which are arranged in this order from the object side. A1F is composed of a movable group A1Fa located on the object side and a fixed group A1Fb located behind it.

The movable group A1Fa is moved by the lens moving means LD in a direction orthogonal to the optical axis L-L and its position is controlled. Although illustration is omitted, as a control system for detecting the tilt of the optical system A and controlling the movement of the movable group A1Fa, for example, the pitch or roll of the optical system A is detected by a sensor, and its output is output. A configuration in which a signal is processed by a control unit such as a microcomputer and then a control signal is sent to the lens moving means LD to correct the image blur can be mentioned.

FIG. 2 is a schematic view showing a structural example of the optical system A, and shows only the afocal portion A1F of the first group.

The afocal portion A1F is composed of a movable group LS1 having a negative refractive power and a fixed group LS2 having a positive refractive power.

FIG. 4 is a schematic diagram for explaining the effective diameter of the fixed group LS2 when the front lens group in the afocal portion is the movable group LS1 in comparison with FIG.
A lens system e in the drawing is a photographing lens system excluding the afocal portion A1F.

FIG. 4A shows the light rays f1 and f2 when the center of the movable group LS1 is located exactly on the optical axis LL, and FIG. 4B shows that the movable group LS1 is Light rays i1 and i2 when they move in a direction orthogonal to the optical axis L-L as shown by an arrow B are shown. As is clear from the comparison between the two, since the light rays i1 and i2 pass in the vicinity of the light rays f1 and f2, the effective diameter of the fixed group LS2 becomes smaller than in the case of FIG. That is, when the image blur correction is performed by moving the movable group LS1 on the front side, even if the correction amount (that is, the moving amount of the movable group LS1) becomes large, it is difficult for light to escape from the peripheral portion of the fixed group LS2. Tends to become.

Since both the movable group LS1 and the fixed group LS2 constitute an afocal system, it is possible to reverse the relationship between them regarding the refractive power.

That is, as shown in FIG. 3, the movable group LT1 having a positive refractive power may be arranged on the front side, and the fixed group LT2 having a negative refractive power may be arranged behind it.

Next, Examples 1 and 2 according to the present invention will be described.

In the first embodiment, the movable group A1Fa is a negative lens and the fixed group A1Fb is a positive lens, while the second embodiment is
In, the movable group A1Fa is a positive lens and the fixed group A1Fb is a negative lens.

The definitions of the symbols used below are summarized in Table 1 below.

[0030]

[Table 1]

Among the various quantities in Table 1, f, r, and d are the values when normalized to f = 1 in the numerical table described later.

FIG. 5 shows the first embodiment, and the optical system 1A is composed of five lens groups, and the first group G1.
The most object-side afocal part A1F constituting the above is configured such that a fixed positive lens is arranged behind a movable negative lens. The rear group A1R that constitutes the first group G1 is composed of three lenses, the second group G2 has three lenses, the third group G3 has one lens, and the fourth group G4 has two lenses. , The fifth group G5 is composed of three filters, respectively.

In assigning a surface number (this is referred to as "i") to each surface of the lens, it is assumed that the surface number increases by 1 from the object side to the image surface side, and the radius of curvature ri (i
= 1, 2, 3, ...) and the lens interval di (i = 1,
2, 3, ...), the subscript i is defined to increase by 1 from the object side to the image plane side, and the configuration of the optical system 1A is shown in the numerical table below. Is.

[0034]

[Table 2]

In this example, f = 1 to 14, FNO
= 1: 1.65 to 2.64, 2 · ω = 55.7 to 4.1
It has been.

In Table 2, "INFINITY" indicates that the radius of curvature is infinite, that is, a flat surface, and "STOP" indicated by r15 means a diaphragm. In the blank column of the refractive index N, the refractive index for air is omitted.

"Variable" indicates that the lens is a movable lens that moves in the optical axis direction. In this example, the lens intervals d9, d14, d17, d2
0 is a variable length, and the relationship with the focal length f is shown in the table below.

[0038]

[Table 3]

The lens surfaces with surface numbers i = 2, 4, 17, and 20 have an aspherical shape represented by the following equation, and their aspherical coefficients are shown in the following table. become.
The coordinates of the aspherical surface in the optical axis direction are "Xa", and the distance from the optical axis is "y".

[0040]

[Equation 1]

[0041]

[Table 4]

In this example, the orders of the aspherical coefficients are 4, 6, and 8.
It has been. Further, "e" in the table means exponential expression with base 10.

The light ray c1 in FIG. 5 is moved by moving the second lens in the direction of arrow B with respect to the light incident on the lens system 1A at an angle θ with respect to the optical axis L-L. The optical path when the image blur correction is performed along L is shown.

Similarly to the light ray d shown in FIG. 8, the light ray d1 is obtained by performing ray tracing so as to satisfy the conditions regarding the passing position on the effective light-receiving surface and the diaphragm surface. Object-side surface of the second lens (surface number i =
The effective diameter is twice the height h1 of the intersection A1 with 3).

FIG. 6 shows a second embodiment, in which the optical system 1B is composed of five lens groups, the first group G1.
The afocal portion A1F on the most object side, which is configured by, is configured by arranging a fixed negative lens behind a movable positive lens. Then, the rear group A1R forming the first group G1 is 3
The second group G2 is composed of three lenses, the third group G3 is composed of one lens, the fourth group G4 is composed of two lenses, and the fifth group G5 is composed of three filters. ing.

As in the case of Embodiment 1 described above, the table below shows the configuration of the optical system 1B in a numerical table by defining the surface number of the lens, the radius of curvature of each surface, and the lens interval.

[0047]

[Table 5]

In this example, f = 1.1 to 15.
5, FNO = 1: 1.65 to 2.64, 2 · ω = 51
It is 3.7. Also, in Table 5, "INFINIT
The meanings of “Y”, “variable” and the like are as described above.

In the second embodiment, the lens spacing d
9, d14, d17, and d20 are variable lengths, and the relationship between these and the focal length f is the same as in Table 3 above. The lens surfaces with surface numbers i = 2, 4, 17, 20 are aspherical, and their aspherical coefficients are as shown in Table 4 above.

The light ray c2 in FIG. 6 is the second ray with respect to the light incident on the optical system 1B at an angle θ with respect to the optical axis L-L.
By moving the lens in the direction of arrow D, the optical axis L
The optical path when the image blur correction is performed along −L is shown.

Similarly to the light ray d shown in FIG. 8, the light ray d2 is obtained by performing ray tracing so as to satisfy the conditions regarding the passing position on the effective light receiving surface or diaphragm surface. Object-side surface of the second lens (surface number i =
The effective diameter is twice the height h2 of the intersection A2 with 3).

The table below shows f when the correction angle θ = 1.16 ° for the optical systems 1A and 1B according to the present invention and the optical system a (the construction surface is the same as the numerical table 3). 1
The amount of movement m of the movable lens (the first lens in the optical systems 1A and 1B and the second lens in the optical system a) when normalized to (the upper side is the positive direction and the lower side is the negative direction), and the second lens. It is shown by comparing with the lens effective diameter φ of (rear side).

[0053]

[Table 6]

Second sheet in optical system 1A, 1B (rear side)
It can be seen that the lens effective diameter φ of is smaller than the lens effective diameter of the optical system a.

In comparison of the optical systems 1A and 1B, it is advantageous for the movable lens of the afocal part to be a biconvex lens in terms of the total length of the optical system. This is because the rear lens group of the afocal part is a positive lens and the object side surface is convex, so that the fixed lens located in front of it is a biconcave lens, whereby the lens interval can be made smaller.

On the contrary, regarding the angle of view, it is advantageous to use a biconcave lens as the movable lens of the afocal portion. this is,
This is because the focal length becomes long when the movable lens is a biconvex lens.

FIG. 7A shows the taking lens e, its focal point F1, principal point H1, and focal length f1. FIG. 7B shows the case of the optical system 1B in front of the taking lens e. Similarly, the focal point F2, the principal point H2, and the focal length f2 when the biconvex lens and the biconcave lens are arranged in this order from the front are shown, and FIG. 7C shows the optical system 1A in front of the taking lens.
As in the case of, the focus F3, the principal point H3, and the focal length f3 when the biconcave lens and the biconvex lens are arranged in this order from the front are shown.

When the biconvex lens is arranged on the front side as shown in FIG. 7B, the focal length becomes long and the angle of view becomes small. However, as shown in FIG. 7C, the biconcave lens is arranged on the front side. Then, the focal length is shortened and the angle of view can be increased.

[0059]

As is apparent from the above description, according to the first aspect of the invention, the front lens group in the front group of the afocal system is the movable group, and the fixed group is arranged behind it. Even when the amount of movement of the movable group is large, it is difficult for light to escape from the peripheral edge of the lens of the fixed group, so the effective diameter of the lens relating to the fixed group can be reduced.

According to the second aspect of the invention, the movable group is a positive lens and the fixed group is a negative lens, whereby the lens interval between the fixed group and the rear group having a positive refractive power is shortened,
As a result, the total length of the optical system can be shortened.

According to the third aspect, by using the negative lens as the movable group and the positive lens as the fixed group, it is possible to shorten the focal length of the system and obtain a large angle of view.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a basic configuration of an image blur correction variable magnification optical system according to the present invention.

FIG. 2 is a diagram showing an example in which the movable group of the afocal portion is a negative lens and the fixed group is a positive lens in the image blur correction variable magnification optical system according to the present invention.

FIG. 3 is a diagram showing an example in which the movable group of the afocal portion is a positive lens and the fixed group is a negative lens in the image blur correction variable magnification optical system according to the present invention.

4A and 4B are schematic diagrams for explaining an effective diameter of a movable lens in the optical system of FIG. 2, where FIG. 4A is a movable group LS.
1 shows the state where the center of 1 is just located on the optical axis L-L, and (b) shows the state where the movable lens LS1 has moved in the direction orthogonal to the optical axis L-L.

FIG. 5 is a diagram showing a configuration of Example 1A according to the present invention.

FIG. 6 is a diagram showing a configuration of Example 1B according to the present invention.

FIG. 7 is a schematic diagram for explaining the advantage of using a biconcave lens as the movable lens in the front group of the afocal system.

FIG. 8 is a diagram showing a conventional configuration example.

FIG. 9 is a diagram for explaining a conventional problem.

[Explanation of symbols]

 A Image blur correction variable magnification optical system A1 First group A1F Afocal part (front group) A1Fa movable group A1Fb Fixed group A1R Rear group LD lens moving means 1A, 1B Image blur correction variable magnification optical system

Claims (3)

[Claims] 1. A first group which is immovable in the optical axis direction,
In an image blur correction variable magnification optical system in which a variable power group following the first lens group is arranged in this order from the object side, the first lens group includes a front lens group of an afocal system and a rear lens group having a positive refractive power. The front group is composed of a movable group and a fixed group arranged behind the movable group, and the movable group is moved in a direction orthogonal to the optical axis by the lens moving means when the variable power optical system is tilted. An image blur correction variable magnification optical system characterized by that. 2. The image blur correction variable magnification optical system according to claim 1, wherein the movable group is a positive lens and the fixed group is a negative lens. 3. The image blur correction variable magnification optical system according to claim 1, wherein the movable group is a negative lens and the fixed group is a positive lens.