JPS63204227A - Variable magnification optical device - Google Patents

Abstract

PURPOSE:To correct an image blur at a telephoto end by displacing an extender lens intersecting orthogonally with the optical axis according to a signal for compensating an image blur which is received from an image blur detector while the extender lens is mounted. CONSTITUTION:The extender lens 5 is put in an optical path of photography after wide-angle photography, and then a deviation detector 7 and an actuator 8 are actuated. The deviation detector 7 detects the inclination of a camera when the camera slants by being applied with an external force and outputs an electric signal corresponding to the quantity of movement of the extender lens 5 perpendicular to the optical axis so as to stop an image of a body on an image plane. The actuator 8 moves the extender lens 5 according to this electric signal, so a photographic lens 5 refracts photographic luminous flux in such a direction that the movement of the image is canceled and stops the image. Thus, the image blur is easily corrected at the telephoto end of the variable magnification optical system where the influence of a hand shake increases abruptly at the telephoto end.

Description

[Detailed Description of the Invention] The present invention is a camera or an interchangeable lens that uses an extender lens as a master lens to change the magnification and also provides image stabilization to prevent image blurring even when external force is applied. Related to optical devices.

[Prior art]

Conventionally, as shown in FIG. 4(A), wide-angle photography has been possible with the built-in extender 5 retracted outside the effective light beam on the image side of the master lens 4, and while the master lens is moved forward. Insert the built-in extender 5 into the light beam using the switching lever 2 (Fig. 4 (C)) to obtain the telephoto end where the focal length of the master lens is expanded (Fig. 4 (B)).
)) cameras are known (Japanese Patent Laid-Open No. 61-2311
No. 0).

Further, as shown in Fig. 5(A), wide end photography is possible with the built-in extender 5 retracted out of the optical path on the image plane side of the master lens 4 of the telephoto lens barrel, and the built-in extender 5 can be switched on with a switching member. An interchangeable lens is known that can be inserted into the light beam of a master lens to obtain a telephoto end with a focal length longer than that of the master lens (Japanese Patent Laid-Open No. 57
-84417).

In this case, if you use an extender that satisfies specific conditions, you can simply insert the built-in extender with the master lens fixed without moving it forward, as in the optical system shown in Figure 4, and the focal length will be expanded and the image plane The position can be an optical system that is held constant.

This type of optical system does not require the trouble of removing the master lens from the camera body and then attaching it, as is the case with regular extenders that are combined with interchangeable lenses, and it is possible to easily switch from wide to telephoto. However, when taking pictures using such a device, image blur tends to occur after switching from the wide end to the telephoto end.

There are many opportunities to take pictures using a still camera or hand-held on a moving car or aircraft that is subject to large vibrations, but in such cases, images tend to be blurred and the image quality deteriorates significantly.

Generally, the longer the focal length f of the photographic lens, the greater the image blur, and the longer the exposure time Δt, the greater the image blur. In other words, the image blur amount d increases in proportion to the focal length f and the exposure time length Δt.

That is, there is a relationship between dcySf and docΔt.

When the built-in extender, which has the function of expanding the focal length of the master lens by 88 times, is inserted into the optical path on the image side of the master lens with focal length fm, the focal length ft of the entire system becomes ft-βa-fm. It is magnified and becomes a lens with a long focal length, but at this time the F of the master lens
The number Fn is also multiplied by 88 to become Ft-βa-Fn.

Therefore, since the lens becomes darker, it becomes necessary to shoot at a slower shutter speed. When an extender is inserted in this way, the focal length becomes longer and the F-number becomes darker, so a slow shutter must be used, which tends to cause image blur due to vehicle vibration or camera shake, resulting in a sharp image. The disadvantage was that it was difficult to obtain. This drawback becomes more noticeable as you increase the magnification of the extender.

In particular, a camera with the structure shown in Figure 4 is applied to a lens shutter camera, but such a camera is called an intermediate model.
A 9-year-old female student who is not used to cameras.

They are often used by elderly people, and it is normal that they cannot be expected to take precautions against camera shake when taking pictures.

However, it is not well known that image blur is many times more likely to occur when shooting at the telephoto end, so there are many cases where works fail due to camera shake when shooting at the tele end. Furthermore, at the wide end, camera shake Z" is not very noticeable, which is not a problem.

For example, if the specifications of the master lens are 35mmF2.8 and the magnification of the extender lens is 2X, if the master lens is moved to the object side using a switching lever (not shown) and the extender lens is inserted into the optical path, the magnification of the extender lens is 70mmF.
It becomes a 5.6 lens. At the telephoto end, the focal length is 2
Since the brightness is reduced by two steps, even if the amount of camera shake is the same as in the original state, the amount of image blur will be affected by eight times (effected by the cube of the magnification). Therefore, although this type of camera provides a lens with a convenient focus, long focal length, and point distance, if you shoot at the telephoto end in the same way as at the wide end, there will be many failures due to camera shake.

Particularly common is image blur that occurs when the camera bows due to the force with which the shutter is pressed at the moment the shutter is released.

However, the trend in lens-shutter cameras is to increase the magnification of the built-in extension, or to switch between three or more stages, thereby increasing the focal length that can be obtained at the telephoto end. It is expected that the number of failures due to camera shake will increase.

As such, currently there are no cameras that are convenient enough for even beginners to easily switch to the telephoto end, and there are no interchangeable lenses that can be fully used.

[Problems to be solved]

The present invention relates to a switching magnification lens or camera that has a built-in extender and can change from the original state (wide) to a state with a long focal length (tele). The objective is to provide an optical system that eliminates the occurrence of image blur that is likely to occur and provides a sharp image.

[Explanation of Examples]

FIG. 1 shows an embodiment of the present invention, in which (A) shows wide-angle shooting, (B) shows telephoto shooting, and (C) shows main parts viewed from above.

■ indicates a mid-range camera body. 4 is a master lens, which is held in a lens barrel that slides back and forth.

An extender lens 5 is arranged on the image side of the master lens 4 and has negative refractive power. In reality, the master lens 4 and the extender lens 5 are usually composed of a plurality of lenses from the viewpoint of correcting aberrations. Reference numeral 2 in FIG. C indicates a switching lever, which is rotatable around a rotating shaft 3 supported by the camera body 1, and has an extender lens 5 fixed to its other end. The switching lever 2 is connected to the holding lens barrel of the master lens 4 by an interlocking mechanism (not shown), and when the master lens 4 is advanced a predetermined amount as shown in FIG. B, the extender lens 5 is inserted into the photographing optical path. Furthermore, when the master lens 4 is retracted, the extender lens 5 is retracted out of the photographing optical path.

It is assumed that play is provided in the interlocking mechanism that drives the switching lever 2 so that the extender lens 5 can freely move by an amount of compensation described later in the inserted state.

6 is a photographing screen, which corresponds to the image receiving surface of the film or image sensor.

7 is a deviation detection device, which has a built-in deviation measuring device such as an accelerometer, angular accelerometer, or speedometer; if it is an accelerometer, the signal is integrated twice to find the amount of deviation at this position;
Based on this, the amount of compensation for the extender lens to prevent image blur is calculated. 8 is an actuator, which can be a solenoid, a meter, a stack of piezo elements, or the like. The actuator 8 is fixed to an auxiliary lever 2' that swings in synchronization with the aforementioned switching lever 2, and a drive rod of the actuator 8 is coupled to the extender lens 5. However, the auxiliary lever 2' is assumed to be firmly locked when the extender lens 5 is inserted.

With the above configuration, after wide-angle photography is performed, when the extender lens 5 is inserted into the photographing optical path, the deflection detection device 7 and the actuator 8 are activated. The deflection detection device 7 detects the movement when the camera is tilted due to an external force, and uses an extender lens 5 to keep the image of the object still on the screen.
Outputs an electrical signal equivalent to the amount of movement of the lens in a direction perpendicular to the optical axis.

Since the actuator 8 moves the extender lens 5 in response to this electric signal, the photographing lens 5 refracts the photographing light flux in a direction that cancels the movement of the image, thereby making the image stationary. In this way, the system is designed to easily compensate for image blur at the telephoto end of the switching variable magnification optical system, where the effects of camera shake suddenly increase at the telephoto end. Since the correction lens group can be shared, a new optical system is not required to perform the function, and it can be achieved in a compact form.

In this example, vibration isolation in the vertical direction has been explained.

This is because most of the vibrations are vertical movements, and in particular camera shake accompanying shutter release is vertical movements. However, more common vibrations,
That is, in order to provide vibration isolation against vertical, horizontal, and diagonal vibrations, the forces of two sets of actuators, one for vertical and one for horizontal, may be applied independently or in a superimposed manner.

The built-in extension optical system according to the present invention corrects image blur by decentering in a direction perpendicular to the optical axis, but if decentering aberration occurs at this time, image quality will deteriorate due to image blur. is corrected, but there is a risk that the image will deteriorate due to decentering aberrations and the correction will be meaningless. Below we will take a closer look at eccentric aberrations caused by the built-in extension lens.

Various aberration theories have been published regarding eccentric aberration when a part of the lens is decentered, but here we will discuss how to handle eccentric aberration coefficients by Matsugen, which was presented at the 23rd Annual Meeting of the Society of Applied Physics in 1962. Explain according to the following.

According to this, the aberration Δ′Y when the built-in extension optical system is parallel decentered by E is caused by the aberration ΔY that exists before the eccentricity of the entire system and the eccentricity of the extension optical system, as shown in equation (a). It is expressed as the sum of eccentric aberrations ΔY (E). As shown in equation (b), eccentric aberration ΔY (E) includes eccentric comatic aberration (IIE), eccentric astigmatism (IIIE), eccentric curvature of field (PR), and eccentric distortion aberration (VEI). , eccentric distortion additional aberration (VB2), and origin movement (8E).

(IIE) to (ΔE) are generally expressed in complex forms that include many terms, but they consist of two lens groups: a fixed lens group (here, the master lens) and a movable lens group (here, the extending optical system). When applied to the present invention in which the movable lens group is parallel and decentered, the light rays αP, αP incident on the movable lens, that is, the built-in extender, and the aberration coefficients Ip, Ilp, Up, of the movable lens group are:
Using Pp and Vp, equations (C) to (h) can be expressed.

Δ′Y−ΔY×ΔY(E)
(a) +2R(N, tan ω
) ((2cos (φ2−φ, ) +CO3(φ1
keφ,))(IIE)=-αP II p+a pIp
(c) (HE)=-αpII[p+a
plIp (d) (PE) = -apP
p (e) (VE], )=-
αpvp Juukou pmp (f) (VB2)
= −a pPp (g)(Δ
E) Knee 2 (α'R - αp) (h) From these formulas, in order to reduce eccentric aberration when the built-in extender optical system is decentered for image blur correction, the spherical surface of the built-in extender optical system must be Formulas (c) to (b) are used to correct aberrations, coma, astigmatism, and Petzval.
), the correction can be made to cancel by bridging the paraxial values αp and ap. Such aberration correction, especially the former correction, has a vector matching with the aberration correction as a built-in extender, and a high-quality switching variable magnification optical system and a high-quality image blur correction lens can be obtained.

The switching magnification optical system according to the present invention divides the entire system of the built-in extender optical system into two lens groups, one of which is a fixed lens group and the other lens group is a movable lens that is movable in a direction perpendicular to the optical axis. A system in which image blur is corrected as a group is also possible.

For example, as shown in Fig. 2 (A), the built-in extender optical system is composed of two negative lens groups 5a and 5b, one of which is fixed as the fixed lens group 5a, and the other with a direction perpendicular to the optical axis. The movable lens group 5b is movable, and an acceleration sensor 7 detects image blur, and an actuator 8 drives the movable lens group to correct the image blur. In this case, the lens group 5a on the master lens side may be a movable lens group, and the lens group 5b on the image side may be a fixed lens group.

When correcting image blur by decentering the entire extender optical system as shown in Figure 4, the relationship between the amount of image movement Δy and the amount of lens movement ΔyA is Δy=(1-βa)Δya, and the amount of image movement Δy of the extender lens is It is determined once the magnification rate (magnification βa) is given. If the structure is as shown in FIG. 2(A), the magnification of the movable lens can be changed, and Δy-(1-β
a2) If the ratio of Δy and ΔyA expressed by ΔYa2 is set to a small value, the influence of the error in the amount of movement perpendicular to the optical axis of the lens on the error in the amount of image movement can be reduced, resulting in rough driving accuracy and stability. Get better. In addition, since the power of each lens group can be reduced, when the lens group on the master lens side, where the occurrence of aberrations, especially spherical aberration and coma, is small, is used as a movable lens group, Δy-(1-βa,)・βa2・Δ
It is expressed as ya2.

On the other hand, the entire system of the extension optical system is arranged so that the positive lens group and the negative lens group from the master lens side or the negative lens group and the positive lens group from the master lens side are arranged so that the entire system has negative power. An extender structure in which one side is driven in a direction perpendicular to the optical axis by an actuator is also possible. In FIG. 2(B), the positive lens group 5a on the image side is driven to correct image blur. The structure shown in FIG. 2(B) has good drive performance because the direction in which the image is moved to correct image blur is the same as the direction in which the movable lens group 5-2 is moved. Further, the ratio of Δy and Δya can be made small, and the drive accuracy is characterized by being rough. Furthermore, when the two lens groups are arranged in this order, the principal point of the entire extender system can be moved closer to the master lens, so even with the same magnification, the power of the extender optical system can be made more relaxed, which reduces aberrations. The occurrence of spherical aberration and Petzval, especially in one direction, is small.

When a piezoelectric element such as a piezo is used as an actuator, the amount of drive is small even if the actuator is multistage, so an optical system is required that has a large amount of image movement relative to the amount of lens movement. In this case, the power arrangement of the negative lens group 5a as shown in FIG. It is good if it is movable. In this case, the same effect can be obtained even if the lens is configured of a positive lens group and a negative lens group from the master lens side, and the image blur is corrected by the negative lens group on the image side.

In this way, if the extension optical system is divided into two lens groups and one lens group performs image blur correction, it is possible to obtain the optimum ratio of Δy and Δya for the actuator.

Furthermore, as shown in Figure 3 (λ) and (B), the extension optical system is divided into three lens groups, and the middle lens group or both end lens groups are moved in a direction perpendicular to the optical axis to correct image blur. A structure that does this is also possible.

In the case of the method shown in Figure 3 (A), the amount of movement ΔYa of the movable lens group
The relationship between z and the amount of image movement Δy is expressed as Δy-(1-βa2)βa3・Δ3'a2,
If the expansion rate of the extender is βa, then βa=βa1・
Considering βa2 and βa3, the ratio of Δy and Δ5'a2 can be selected more freely than in a two-group configuration, and aberrations can be corrected better.

In the case of Fig. 3 (B), the movable lens group Δya+++ΔYa3
The relationship between the image movement amount Δy and the image movement amount Δy is Δy−(1−βa+)βa2′βa3”Δya,+(1
−βa3)′Δya3, and further Δy and ΔYa
Since the relationship between k and Δya3 can be freely selected, aberration correction can be further improved.

Furthermore, by moving two separate lens groups, the 5a lens group and the 5c lens group produce decentering aberrations in opposite directions, thereby making it possible to mutually correct eccentric aberrations and easily reduce the occurrence of decentering aberrations.

In addition, the following modifications are possible. The movement in the direction perpendicular to the optical axis includes linear movement in addition to rotation around a certain rotation center as described in the second section.The deviation detector may use a gyro in addition to an acceleration sensor. It is also possible to use a gyro and connect it directly or indirectly to the movable lens group, but in that case the actuator 8 can be omitted. Using an aspherical surface in the fixed lens group or the movable lens group of the built-in extender lens allows the structure to be constructed with a smaller number of lens elements, helping to reduce the weight of the movable lens group and improve driveability.

In addition to its function as an image stabilization lens, the extender lens can also be structured to perform micro focusing by moving the extender lens group, or it can be configured with multiple lens groups to perform image stabilization and micro focusing differently. It may also be a built-in extender lens that has the functions handled by the lens group. Such a lens can be used as a macro lens that can obtain even greater image magnification from close range at the telephoto end.

An image forming element and a light receiver may be used on the image plane side of the built-in extender to detect image blur through the entire system, and the extender may be driven to eliminate image blur.

It may be incorporated into the interchangeable lens 9 shown in FIG. 5, and in that case, the deflection detection device may be located on the camera body 10 side.

〔effect〕

In a switching variable magnification optical system where the influence of camera shake suddenly increases at the telephoto end, it is possible to realize a system that can correct image blur at the telephoto end and obtain high image quality at both the wide and telephoto ends.

The system described above can be made more compact because the built-in extender lens and image stabilization lens, which are originally required for zooming, can be used in common, eliminating the need for additional optical elements.

If the switching member is used as a driving member for the correction lens, the number of mechanical parts can be reduced and the structure can be simplified.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, in which (A) is a cross-sectional view showing the state of wide shooting, and (B) is a sectional view showing the state of telephoto shooting.
(C) is a plan view of the main part. 2 (A) (B) and 3 (A) (B) are sectional views showing a modified example, FIG. 4 shows a conventional example, (A) (B') are sectional views, ( C) is a front view. FIGS. 5A and 5B are cross-sectional views of another conventional example. In the figure, 1 is a camera, 2 is a switching member, 3 is its fulcrum,
4 is the master lens, 5 is the built-in extender lens,
6 is a film surface, 7 is a shake detector, 8 is an actuator, 9 is a switching variable magnification lens, and IO is a camera.

Claims (2)

[Claims] (1) In a device that performs magnification by inserting and removing an extender lens on the image plane side of the master lens via a switching member, compensate for image blur from an image blur detection device with the extender lens inserted. A variable magnification optical device characterized by having a configuration in which an extender lens is displaced in a direction perpendicular to an optical axis according to a signal. (2) The variable magnification optical device according to claim 1, wherein the switching member for inserting and removing the extender lens is used as a support member for the extender lens when compensating for image blur.