JP3193387B2 - Tilt zoom lens system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens used for a camera or the like, and more particularly to a subject plane inclined with respect to a main optical axis (an optical axis perpendicular to the center of an imaging plane of a photographic film or the like; The present invention relates to a tilt zoom lens system capable of focusing on a zoom lens.

[0002]

2. Description of the Related Art Conventionally, in photographing with a camera or the like, tilting photographing is performed in order to focus a subject inclined with respect to a main optical axis. The conditions for this tilt shooting are:
It is required that the extension of the plane of the subject, the extension of the plane including the principal point of the lens system, and the extension of the plane of the photographing film intersect in a straight line. Therefore, in order to perform photographing with a camera in which the photographic film plane is fixed to the camera body, such as a single-lens reflex camera,
The lens system is configured to be tilted with respect to the main optical axis, and while adjusting the tilt angle of the lens system, the angle at which the camera body faces the subject, that is, the angle formed by the main optical axis with the subject, is adjusted. The change may be adjusted. As described above, if the angle of the main optical axis with respect to the subject is adjusted by adjusting the direction of the camera body while tilting the lens system with respect to the main optical axis, the subject can be tilted when the above-described tilting shooting condition is satisfied. Can be focused.

[0003]

A lens system having a single focal length has been conventionally proposed as a lens system capable of performing such tilting photographing. However, a zoom lens capable of changing the focal length cannot perform tilting shooting. A possible lens system has not yet been proposed. SUMMARY OF THE INVENTION It is an object of the present invention to provide a tilt zoom lens system capable of tilting photographing with a zoom lens. Another object of the present invention is to provide a tilt zoom lens system in which the center of a subject image does not move with respect to the main optical axis even during zooming.

[0004]

According to the tilt zoom lens system of the present invention , at least two or more lenses are used during zooming.
Lens group is moved on the main optical axis,
A lens having a zooming function among the two or more lens groups
Behind the lens group on the object side and than fixed group than the group
When there is constituted by the tilt group, a lateral magnification of the tilt unit and m _T, and the distance from the tilt center to the first principal point and a second principal point of the tilt unit and each L _1, L _2,
The tilt group is moved forward so that L ₂ / L ₁ = m _T is satisfied.
It is characterized in that it can be tilted with respect to the main optical axis.
I do .

[0005]

Next, the present invention will be described with reference to the drawings. FIGS. 1A and 1B are diagrams for explaining the basic concept of the present invention using a thin lens system. FIG. 1A shows the short focal length side, and FIG. 1B shows the long focal length side. In these figures, O is subject, F _P is the lens system the image plane of the photographing film in camera or the like is disposed, ZL is a zoom lens system. The zoom lens system ZL is comprised of two groups here, it is tiltably constituting the optical axis X _T with respect to the main optical axis X of the zoom lens system ZL of the first lens group as a tilt group T. Further, the second lens group is defined as a variable power unit V and has a main optical axis X.
The zoom lens system ZL is configured to be movable in the front-rear direction along with the zoom lens system ZL so as to perform zooming by changing the focal length of the entire zoom lens system ZL. Then, when the object O is tilted α degrees with respect to the main optical axis X, that is inclined θ degrees with respect to the main optical axis X of the optical axis X _T of the tilt group T, the focus of the object image I _T F imaged so as to be parallel to the image plane F _P to _T, imaging at the required magnification of an object image I _T as a subject image I by moving back and forth zooming group on the main optical axis X on it Plane _FP
An image is formed in focus. Here, the tilt group T is tilted so that the subject image _IT is focused at the focal point F _{T on} the imaging plane F
Since by parallel imaging and _P is performed focusing can hold an in-focus state with respect to subsequently move the zooming group V inclined on the imaging plane F _P even when subjected to zooming the object plane .

Incidentally, FIGS. 2A and 2B show conceptual diagrams on the short focal length side and the long focal length side when the zooming unit V is tilted without tilting the tilt group T, respectively. ,
When the zooming group V is tilted, the relationship between the angle α of the tilted object O and the tilt angle θ of the zooming group V is tan α = (β ₁ −β ₂ ) / β ₀ · tan θ. Is transformed, tan α = 1 / m _T (1-1 / m _v ) tan θ, and therefore tan θ = m _T / (1-1 / m _V ) · tan α. Here, m _T is the lateral magnification of the tilt group T, m _V is the lateral magnification of the variable power group _V , and this lateral magnification m _V is given by m _V = m from the focal length f of the entire system and the focal length f _{T of the} tilt group. It is determined by the _f / f _T. Therefore, when the zooming unit V is tilted, it is necessary to zoom by changing the focal length and the lateral magnification of the zooming unit V, and at the same time, change the tilt angle θ to perform focusing. This is not preferable because the shooting operation is complicated.

FIG. 3 is a view showing a tilt group T in the zoom lens system of FIG. 1 as a thick lens system.
Are tilted around the point P. Then, the point P is matched to the second principal point of H ₂ tilt group T. H ₁ is the first principal point of the tilt group.
Thus, by tilting the tilt group the second principal point H ₂ as the center P, the focus F _T the object image I _T
As long as the keep is focused on, it is also retained in-focus state by zooming by Henbaigun V, and never image I is moved on the image plane F _P by zooming simultaneously.

FIG. 4 shows a first example of the zoom lens system ZL.
In this example, the lens group is composed of a plurality of lens groups. FIG. 1A shows the short focal length side, and FIG. 2B shows the long focal length side, each showing a thin lens system. In this embodiment, the first lens group is composed of a fixed lens group A and a tilt group T, and only this tilt group T is tilted for photographing. Optical axis X
Zooming is done by moving it up. Also in this zoom lens system ZL, a lens group constituted by a part of the first lens group disposed in front of the zooming unit V is configured as a tilt group T, and by tilting this, the subject image I _T a can be parallel to the imaging and the imaging plane F _P to focus F _T, it is possible to hold an in-focus state of the image I even when performing zooming by Henbaigun V.

FIG. 5 is a diagram showing the lens system of FIG. 4 as a thick lens system. A fixed lens group A disposed on the front side and a tilt group T disposed on the rear side constitute a first lens group. .
The on-axis paraxial inclination angles of the light incident on and outgoing from the fixed group A, the tilt group T, and the variable power group V are respectively β ₀ , β ₁ , β
₂ , β ₃ . Further, tilt group T is rotated in the vertical direction shown around the first principal point H ₁ and a second principal point H _2, and the point P on the main optical axis, the optical axis of the tilt group T X _T
Is configured such that the inclination angle θ with respect to the main optical axis X can be arbitrarily changed.

Now, as shown in FIG. 6, the tilt group T is inclined at an angle θ about a point P at a distance from the first principal point H ₁ to L _{1 and at} a distance from the second principal point H ₂ to L _2. Consider the case. The tilted, first principal point H ₁ is ', the second principal point H ₂ is the point H _2' points H ₁ and that is moved to. The image I _A formed by the fixed group A at the focal point F _A becomes the image I _T formed by the tilt group T at the focal point F _T. Here, the image I _A
Let F _A be a point on the optical axis of an image I _T corresponding to this point F _A
Is referred to as F _T '. At this time, the point H ₁ from the point H ₁ 'height h ₁ of h ₁ = L ₁ theta, and the point H ₂ from the point H _2' height h ₂ of the h ₂ = L ₂ theta. Also, triangular displacement height Delta] h ₂ of the image I _T which affects the image I _A by the height movement h ₁ of the first principal point H ₁ is the image I _A and the first principal point H ₁ 'constituting
When, the triangles constituting the the image I _T second principal point H ₂ 'similar figures
, And the addition, F _A and configuration first principal point H ₁ 'Points of Field I _A
And triangles, points F _T of the image I _T corresponding to the point F _A '
And the triangle formed by the second principal point H ₂ ′ is similar
Because, F _T 'second point of the image I _T corresponding to the point F _A of the image I _A
The length Δh ₂ deviating from the principal point H ₂ ′ is Δh ₂ : I _T = h
_{1: I A, Δh 2 = I T} / I A · h 1 , and the case
Where m _T is the lateral magnification in the tilt group T, and m _T = β
₁ / β ₂ , ie, m _T = I _T / I _A ,
h ₂ = m _T · h ₁ Thus, the axial displacement amount y of lateral to the main optical axis S of the image I _T is y = h ₂ -Δh ₂
Which can be rewritten as y = L ₂ θ−m _T · h ₁
Next, further, it becomes _{y = L 2 θ-m T} · L 1 θ. What
Since h ₁ and h ₂ have positive values in the upward direction in the figure,
Δh ₂ is a negative value. Therefore, axial shift amount of the image I _T
The order to zero, i.e., the light point F _T 'in the image I _T
In order to locate at the point F _T on the axis , y = 0 may be set.
From this, the equation y = L ₂ θ−m _T · L ₁ θ is modified.
And y = (L ₂ −m _T · L ₁ ) θ, and L ₂ = m _T ·
L ₁ , that is, L ₂ / L ₁ = m _T is derived.

Therefore, if the tilt group is tilted around the point P which satisfies the condition L ₂ / L ₁ = m _T , the subject image I _T can always be formed at the focal point F _T , does not image M is moved on the image plane F _P by. Moreover also retained focus state by zooming by zooming group, and never image M is moved on the image plane F _P by zooming simultaneously.

[0012]

As described above, the present invention provides a zoom
At least two or more lens groups move on the main optical axis during
In a zoom lens to be moved, the two or more lenses
Lens in front of lens group with zoom function
Group consists of a fixed group and a tilt group behind it
The horizontal magnification of the tilt group is set to m _T , and the tilt
From the center to the first and second principal points of the tilt group
When the distances are L ₁ and L ₂ , respectively, the tilt group is L ₂ / L ₂
L ₁ = m and satisfy the relationship of _T By configured to tilt, it is possible to tilt photographed by tilting operation
And keep the in-focus state even during zooming.
In addition to the above, the image does not move even when both tilting and zooming are performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a thin lens system according to a reference example of the present invention.

FIG. 2 is a configuration diagram of an example of a thin lens system that is not preferable compared to the reference example .

FIG. 3 is a configuration diagram of a thick lens system for explaining a tilt center of the tilt group in FIG. 1;

FIG. 4 is a configuration diagram of a thin lens system according to a first example of the present invention.

FIG. 5 is a configuration diagram of a thick lens system in a first example .

FIG. 6 is a configuration diagram for explaining a tilt center of a tilt group in FIG. 5;

[Explanation of symbols]

ZL zoom lens system T tilt unit V Henbaigun X main optical axis O subject H ₁ first principal point H ₂ second principal point P tilt center

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takayuki Ito 2-36-9 Maeno-cho, Itabashi-ku, Tokyo Asahi Optical Industry Co., Ltd. (56) References JP-A-61-95308 (JP, A) 51-260 (JP, Y1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04 G03B 5/00-5/08

Claims (1)

(57) [Claims] (1) at least two or more lenses during zooming;
In a zoom lens where the lens group is moved on the main optical axis
Of the two or more lens groups having a zooming function.
A fixed group the lens group in front than lens group than
Constituted by a tilt group at the back, the lateral magnification of the tilt unit and m _T, respectively L ₁ the distance from the tilt center to the first principal point and a second principal point of the tilt group, when the L ₂ the tilt so as to satisfy L ₂ / L ₁ = m _T
That the group is tiltable with respect to the main optical axis.
Features a tilt zoom lens system.