JP2584857B2 - Shooting lens - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens for a television camera, and more particularly to a zoom lens capable of macro photography and tracking adjustment.

(Prior art)

2. Description of the Related Art Conventionally, a technique of moving a relay lens group of a zoom lens in order to sharply form a subject image formed by a television interchangeable lens detachable from a camera body on an imaging surface of the television camera body. So-called tracking adjustments are known.

Also, a technique for moving a relay lens group in the same manner when performing macro shooting is known.

By the way, in Japanese Patent Publication No. Sho 58-1401, after moving the same relay lens group along the optical axis and moving the relay lens group to perform macro photography in order to enable macro photography and tracking adjustment, There is proposed a technique for returning the relay lens group to the original tracking position where the tracking has been adjusted again when shifting to the normal shooting mode.

[Problems to be solved by the present invention]

However, in the above-mentioned Japanese Patent Publication No. 58-1401, a macro photographing mechanism, a tracking adjustment mechanism, and a mechanism for interlocking these two mechanisms are used in order to make each relay lens group use each function. It is necessary to provide

Therefore, while the mechanical structure becomes complicated and large, the mechanisms for returning the lens units for tracking adjustment must have precise accuracy.

An object of the present invention is to provide a photographing optical system for solving the above-mentioned problems.

[Means and structure for solving the problem]

In a lens group including a focusing unit and a variable power unit in order from the object side, a photographing lens configured by a relay lens group consisting of a front group and a rear group with the longest air interval performing an imaging action,
The rear group includes a first movable lens group that moves in order from the object side along the optical axis for macro photography, a fixed lens group having a negative refractive power, and an optical axis that has a positive refractive power and performs tracking adjustment. And the focal lengths of the rear group of the relay lens group, the first movable lens group, the fixed lens group, and the second movable lens group are f _R and f _M , respectively. , f _N , f _F, and when the distance from the rear principal point of the second movable lens group to the image plane is B, 0.9 <f _M / f _R <1.9 0.8 <f _F /B<1.8 −2.9 <F _N / f _R <-0.9, while the rear group is a fixed lens group having a positive refractive power in order from the object side, and the first movable unit that moves along the optical axis for macro photography. Lens group, fixed lens group with negative refractive power, move along optical axis for tracking adjustment with positive refractive power When configured in 2 movable lens group, the rear group of the relay lens group, the first movable lens group, a fixed lens group having negative refractive power, the second movable lens group having a focal length of each f _R , f _M , f _N , f _F and the distance from the rear principal point of the second movable lens group to the image plane is B, 0.9 <f _M / f _R <1.9 0.8 <f _F / B < 1.8 −2.2 <f _N / f _R <−0.7.

〔Example〕

FIGS. 1, 3, 5, and 7 are lens cross-sectional views at the wide-angle end of each of Numerical Examples 1, 2, 3, and 4 according to the present invention.

G ₁ has a positive refractive power and is a focusing lens group that is movable in the optical axis direction for focusing, and lens groups G ₂ and G ₃ are zoom lens groups for zooming. ₂ has a negative refractive power and moves along the optical axis during zooming to act as a variator, and G ₃ has a negative refractive power and compensates for image plane movement during zooming. Acts as Also, G ₄ is a relay lens group to fulfill the imaging action. This relay lens group G ₄ is located on the object side with the longest air gap,
₄₁ , a relay rear group _G42 is arranged on the image plane side. Incidentally, the space between the rear group G ₄₂ and the front group G ₄₁ is a space capable of using in order to place an optical member extender and the like. In this example, both the front group and the rear group have positive refractive power. In the sectional view of the lens, P indicates an equivalent of a color separation prism.

Rirerengu group G ₄ of the relay rear group G with respect to the present invention
_42, positive first and movable lens G _M which moves along the optical axis during macro photography has a refractive power, a positive second movable lens that moves along the optical axis during tracking shooting has a refractive power group
And G _F, and is further between the first movable lens group G _M and the second movable lens group G _F, a lens group G _N is arranged having a negative refractive power be fixed. The negative lens group G _N of the fixing is a lens group for suppressing well-balanced aberration fluctuation when performing macro photographing and tracking adjustment by moving independently of each movable lens.

The first and the movable lens group G _M and the second movable lens group G _F,
As will be described later, they move along a macro cam groove and a tracking adjustment cam groove provided in the lens barrel.

As described above, in the present invention, since the movement of the macro photography and the tracking adjustment are controlled independently, the interlocking mechanism as shown in the related art is not required, and no complication is caused.

Now, conditions for maintaining good optical performance while miniaturizing the optical system according to the present invention, and particularly for properly correcting aberrations when the first and second movable lens groups are moved are described below. .

That is, the focal lengths of the rear group of the relay lens group, the first movable lens group, and the second movable lens group are respectively set.
f _R, f _M, and f _F, when the distance to the image plane and B from a rear principal point of the second movable _{lens, 0.9 <f M / f R} <1.9 ... (1) 0.8 <f F /B<1.8 (2) is to satisfy the following conditional expression.

Expression (1) in each of the above conditions is a condition regarding the focal length f _M of the first movable lens group that moves during macro shooting and the focal length f _R of the rear group of the relay lens, and is set to an appropriate power of the first movable lens group. This is a condition for enabling macro focusing, while maintaining good optical performance while reducing the size. If the lower limit is exceeded, the power of the first movable lens group becomes too strong.
It becomes difficult to suppress fluctuations such as coma. On the other hand, the amount of movement of the first movable lens group G _M becomes too large when performing the macro focusing exceeds the upper limit, the lens system becomes bulky.

Conditional expression (2) is a condition in which the focal length f _F of the second movable lens group that moves during the tracking adjustment and the distance B between the rear principal point of the second movable lens group and the image plane change the aberration with respect to the tracking adjustment amount. It is desirable to make the entire lens system closer to the object side than the second movable lens group closer to the afocal point for aberration correction. If the lower limit is exceeded, the lens system closer to the object side than the second movable lens group is relatively. On the other hand, if it exceeds the upper limit, it becomes a relatively strong convergence system. In any case, the fluctuation of spherical aberration, coma aberration, curvature of field, etc. becomes large, and good imaging performance is obtained when tracking is adjusted. It becomes difficult to maintain.

In particular, the first movable lens group G _M for sequentially macro focusing the relay rear group G _42, a fixed lens group G _N where a fixed having negative refractive power, a second movable lens group G _F for tracking adjustment when the focal length of the stationary lens group when composed of three lens groups and f _N, it may satisfy _{-2.9 <f N / f R <} -0.9 ... (3) becomes a condition.

Conditional expression (3) is particularly as follows: the rear group of the relay lens is a first movable lens group having a positive refractive power, a fixed group having a negative refractive power, in order from the object side,
During three-group construction of the second movable unit having a positive refractive power, the conditions relating to the focal length f _R of the group after the focal length f _N and the relay lens of the fixed group of negative refractive power, the negative refractive power exceeds the lower limit power Becomes too weak, the angle difference between the incidence and exit of light rays before and after the fixed group with negative refractive power disappears. If the upper limit is exceeded, the power of negative refractive power becomes too strong. The angle difference between the incidence and emission of light rays before and after becomes noticeable, and in any case, the aberrations, especially spherical aberration and astigmatism, when moving each movable lens for macro photography and tracking adjustment are lost. It becomes difficult to perform both functions well. Further, when the rear group of the relay lens is composed of three groups, it is desirable that the first movable lens group is composed of two convex single lenses and one cemented lens, and the fixed group having a negative refractive power is an image field. It is desirable that the second movable group is composed of one convex single lens or one convex single lens or a single concave lens having a surface with a stronger curvature directed to the side, or a single lens of a cemented positive lens and negative lens. It is desirable that the lens be composed of a laminated lens.

On the other hand, particularly in the case of suppressing aberration fluctuations during macro photography, as shown in FIGS. 5 and 7, the relay rear group _G42 is sequentially arranged in the fixed lens group G _P having a positive refractive power and the macro focusing. the first movable lens group G _M of use, the fixed lens group G _N where a fixed having a negative refractive power may further when configured with the second group of movable lens group G _F for tracking adjustment, at this time, particularly The focal length of the fixed lens group with negative refractive power
when the f _N, may satisfy _{-2.2 <f N / f R <} -0.7 ... (3) ' becomes conditions.

The fixed positive lens _GP partially shares the power of the first movable lens group for macro, while suppressing fluctuations in aberrations in macro focusing. At this time, the conditional expression indicates a desirable refractive power arrangement of the negative fixed lens, and if the upper limit is exceeded, the negative refractive power becomes too strong, and if the lower limit is exceeded, the negative refractive power becomes too weak. In any case, it becomes difficult to balance aberration variation when moving the first and second movable lens groups, particularly spherical aberration and field curvature.

When the rear group of the relay lens is composed of four groups, it is preferable that the fixed group _GP having a positive refractive power is composed of one convex single lens or one cemented lens, and the first movable lens group is composed of one convex lens. It is desirable to constitute a single lens and one cemented lens or two cemented lenses. The fixed group G _N having a negative refractive power is constituted by one concave single lens, and the second movable lens group G _F is constituted by 1
It is desirable that the lens be composed of one convex single lens or one cemented lens. Further, the surface distance between the fixed group having the positive refractive power and the first movable lens group is set such that no useless space is created due to the relationship between the set closest photographing distance and the power of the first movable group.

Next, a structure for moving each movable lens group will be briefly described with reference to FIG. FIG. 9 (B) is a cross-sectional view taken along the cutting line 1 in FIG. 9 (A).

W is fixed cylinder, the fixed lens G _P, linear guide groove for parallel macro focusing and tracking adjustment and the optical axis while holding the G _N and the like are cut. W _M and W _F are the first
The second group of movable lens G _M, the G _F, a rotary cylinder which linear cam groove of the swash moving control are cut through the drive pin P _1, P _2.

Macro shooting, or when performing tracking adjustment, carried out by rotating the rotary cylinder W _M or W _F.

In an embodiment of the present invention described later, first at the first embodiment, when the first movable lens group G _M at macro photographing an object distance at the wide angle end is 10mm from the first lens surface, G _M is -2.08mm Moved and -0.5m of the second movable lens group during tracking adjustment
The image plane movement amount is -0.48 mm with respect to the movement of m.

In the second embodiment, when the first movable lens group G _M is at the wide-angle end and the object distance is 10 mm from the first lens surface, G _M is −3.88 mm.
To move and adjust the tracking of the second movable lens group during tracking adjustment.
The image plane movement amount is -0.47 mm for the movement of 0.5 mm.

In the third embodiment, when the first movable lens group G _M is at the wide-angle end and the object distance is 10 mm from the first lens surface, G _M is −1.18 mm.
To move and adjust the tracking of the second movable lens group during tracking adjustment.
The image plane movement amount is -0.5 mm for the movement of 0.5 mm.

In the fourth embodiment, when the first movable lens group G _M is at the wide-angle end and the object distance is 10 mm from the first lens surface, G _M is -1.93 mm.
To move and adjust the tracking of the second movable lens group during tracking adjustment.
The image plane movement amount is -0.42 mm for the movement of 0.5 mm.

Next, numerical examples of the present invention will be described. In numerical examples
Ri is the radius of curvature of the i-th lens surface in order from the object side,
Is the i-th lens thickness and air gap in order from the object side, Ni
And νi are the refractive index and the Abbe number of the glass of the i-th lens in order from the object side.

As described above, according to the present invention, it is possible to achieve good imaging performance even when the macro shooting distance is as close as -10 mm, and to obtain good imaging performance even during tracking adjustment. .

[Brief description of the drawings]

1, 3, 5, and 7 are lens cross-sectional views of Numerical Examples 1 to 4, respectively, according to the present invention. FIG. 2, FIG. 4, FIG. 6, and FIG. 8 are various aberration diagrams of Numerical Examples 1 to 4, respectively. In the aberration diagrams, (A) is an aberration diagram at infinity shooting at the wide-angle end, (B) is an aberration diagram at infinity shooting at the telephoto end, and (C) is a wide-angle end. (D) is a diagram showing various aberrations at the time of tracking adjustment in infinity shooting at the wide-angle end,
M indicates a meridional image plane, and S indicates a sagittal image plane. FIG. 9 is a view showing a lens barrel according to the present invention. In the figure, G ₄ denotes a relay system, G _M, G _F respectively macro photographing,
This is a lens group for tracking adjustment.

Claims (2)

(57) [Claims] 1. A photographing lens comprising a lens unit including a focusing unit and a zooming unit in order from the object side, and a relay lens unit comprising a front unit and a rear unit with a longest air interval, which performs an image forming operation. Wherein the rear group includes a first movable lens group that moves along the optical axis for macro photography in order from the object side, a fixed lens group that has a negative refractive power, and a tracking lens that has a positive refractive power. And a second movable lens group that moves along the optical axis, and the focal lengths of the rear group of the relay lens group, the first movable lens group, the fixed lens group, and the second movable lens group are respectively f _R, f _M, f _N, and f _F, when the distance to the image plane and B from a rear principal point of the second movable _{lens, 0.9 <f M / f R} <1.9 0.8 <f F / B _{<1.8 -2.9 <f N / f} R < photographing lens satisfies the -0.9 conditional expression. 2. A photographing lens comprising a lens unit including a focusing unit and a variable power unit in order from the object side, and a relay lens unit consisting of a front unit and a rear unit separated by the longest air interval to achieve an image forming action. Wherein the rear group includes a fixed lens group having a positive refractive power in order from the object side, a first movable lens group moving along the optical axis for macro photography, a fixed lens group having a negative refractive power, A second movable lens group that has a refractive power and moves along the optical axis for tracking adjustment, a rear group of the relay lens group, the first movable lens group, and a fixed lens that has the negative refractive power. When the focal lengths of the lens group and the second movable lens group are f _R , f _M , f _N and f _F , respectively, and the distance from the rear principal point of the second movable lens group to the image plane is B, 0.9 <f _M / f _R <1.9 0.8 <f _F /B<1.8 −2.2 <f _N / f _R <−0.7 Shooting lens to be a sign.