JPS5842443B2 - Harmful light blocking device for zoom lenses - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zoom lens having a diaphragm behind a rear lens group that blocks harmful light, and particularly relates to a zoom lens that has a diaphragm behind a rear lens group that blocks harmful light. Relating to a light prevention device.

For example, in a two-group zoom lens, it is difficult to correct flare because the aperture efficiency is too large except when the lens is set to a wide angle.

For this reason, a fixed diaphragm has traditionally been placed near the mount to prevent harmful light from flaring when the lens is set to telephoto.

However, when the focal length is set to an intermediate focal length, flare cannot be effectively blocked, and there is a fear that image deterioration may occur.

The present invention eliminates the drawbacks of the conventional ones mentioned above,
The purpose of this device is to provide a harmful light blocking device for a zoom lens that can effectively block harmful light such as flare in the entire range from wide-angle to telephoto. The diaphragm for blocking harmful light is movable in the direction of the optical axis of the lens, and this diaphragm is connected to the rear lens group, so that the diaphragm moves following the movement of the rear lens group. .

The present invention will be explained below with reference to embodiments shown in the drawings.

FIG. 1 shows a first embodiment of the present invention, and shows a lens barrel 1.
The front lens group 2 and the rear lens group 3 supported by the lens barrel 1 are moved independently in the optical axis direction of the lenses by rotation of a zoom ring 4 attached to the outer periphery of the lens barrel 1 to change the focal length. ing.

In addition, lens group 2.3 by rotating this zoom ring 40 times.
Since the movement is performed by a well-known cam (not shown), a description thereof will be omitted.

An arm 6 projecting rearward from the lens group 3 is provided on the frame 5 supporting the rear lens group 3 with a screw 7, and this arm 6 is concentrically connected to the rear lens group 3. It's curved.

A pin 8 protruding outward is implanted at the tip of the arm 6.

An annular diaphragm 9 is slidably disposed on the outside of the arm 6, and this diaphragm 9 has a diaphragm oblique to the circumferential direction, as shown in detail in FIG. A cam groove 10 is formed, and the pin 8 is slidably fitted into the cam groove 10.

At the rear end of the aperture tool 9, there is an annular aperture 11 that protrudes inward.
is installed protrudingly to block flares.

Further, the diaphragm 9 is arranged concentrically with the rear lens group 3.

On the other hand, a mount frame 12 is fixed to the rear end of the lens barrel 1, and a cylindrical rear cover 13 protruding from the inner end of the mount frame 12 is fitted onto the outer periphery of the diaphragm 9. , the diaphragm 9 can then be slid against the cover 13.

A pin 14 implanted on the outer periphery of the restrictor 9 is slidably fitted into a cam groove 15 formed in the rear cover 13.

This cam groove 15 is formed obliquely with respect to the circumferential direction of the rear cover 13, and in this embodiment, this cam groove 15 is perpendicular to the cam groove 10 of the aperture tool 9, but this cam groove 10, The 150 angle of inclination is determined in consideration of the distance from the rear lens group 3 calculated from the state of occurrence of flare due to lens characteristics.

Incidentally, an aperture ring 16 for a general aperture (not shown) is installed between the front lens group 2 and the rear lens group 3 to adjust the amount of light reaching the film surface by changing the aperture.

Next, the operation of the above-described embodiment will be explained.

As mentioned above, when the zoom ring 40 rotates, the front lens group 2 and the rear lens group 3 move in the direction of their optical axes to change the focal length. At this time, the arm integrated with the frame 5 of the rear lens group 3 6 also moves in the optical axis direction.

If the moving direction of the arm 6 is rightward in FIG. 2, the pin 8 of the arm 6 is fitted into the cam groove 10 of the diaphragm 9, so the diaphragm 9 moves in the direction shown by arrow a in FIG. Try to rotate.

However, since the pin 14 of this diaphragm 9 fits into the cam groove 15 of the rear cover 13, the diaphragm 9 will move diagonally, and as a result, the diaphragm 11 of the diaphragm 9 will be moved toward the lens group 2.
, 3 in the optical axis direction to take a position where flare can be effectively blocked.

Note that the rear cover 13 with respect to the optical axis direction of the lens groups 2 and 3
By changing the angle of the cam groove 150, it is possible to change the forward/backward distance of the diaphragm 9 relative to the rotation angle of the zoom ring 4. In particular, the angle of the cam groove 150 can be changed to
If the zoom ring 4 is made perpendicular to the optical axis direction, the aperture tool 9 can be prevented from moving back and forth even when the zoom ring 4 rotates.

Therefore, depending on the characteristics of the lens group 2.degree. 3, the angle of the cam groove 150 can be changed midway so that the aperture 11 of the aperture tool 9 is positioned at a position where flare can be blocked to the maximum extent.

3 to 5 show a second embodiment of the present invention, but the same configuration as the first embodiment described above is
The same reference numerals are given in the drawings, and the explanation thereof will be omitted.

A long groove 1T extending in the longitudinal direction of the lens groups 2 and 3 is formed in the diaphragm 9 equipped with the diaphragm 11.
A pin 8 of the arm 6 is slidably fitted into the arm 6 .

Further, the rear cover 13 of the mount frame 12 is provided with the aperture tool 9.
A long groove 18 in the longitudinal direction shorter than the long groove 17 is formed, and a pin 14 of the aperture tool 9 is slidably fitted into this long groove 18.

A tension spring 19 is interposed between the pin 14 of the diaphragm 9 and the rear cover 13, and urges the diaphragm 9 toward the rear side of the lens barrel 1.

According to the above-described configuration, the focal length changes by rotating the zoom ring 40, but at this time, the frame body 5 also rotates the rear lens group 3.
and move in the direction of its optical axis.

Therefore, if the frame body 5 were to move to the right in FIG. do.

As a result, the diaphragm 11 of the diaphragm 9 moves to a position that effectively blocks flare according to the characteristics of the lens groups 2 and 3.

In this way, as the frame 5 moves to the right, the squeeze tool 9 also moves to the right due to the action of the spring 19, but the squeeze tool 9
Since the long groove 17 of the rear cover 130 is longer than the long groove 18 of the rear cover 13, when the pin 8 of the arm 6 is located at the center of the long groove 17 of the diaphragm 9, the pin 14 of the diaphragm 9
As a result, the diaphragm 9 can no longer move to the right even if it is pulled by the spring 19.

Then, only the frame 5 moves and the diaphragm 9 stops, but this is necessary depending on the characteristics of the lens groups 2 and 3.

Note that when the frame 5 is pulled to the left by rotation of the zoom ring 4, the aperture tool 9 is pulled to the left against the spring 19.

As explained above, the harmful light blocking device for a zoom lens according to the present invention allows the aperture to move in the optical axis direction of the lens, connects the aperture with the rear lens group, and controls the movement of the rear lens group. Since the aperture moves accordingly, by setting the distance the aperture moves relative to the distance the rear lens group moves according to the characteristics of the lens, harmful light such as flare can be eliminated in all ranges from wide-angle to telephoto. It has excellent effects in that it can block well and provide high-quality images.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a first embodiment of a harmful light blocking device for a zoom lens according to the present invention, FIG. 2 is an explanatory diagram of the main part of FIG. 1, and FIG. 3 is a zoom lens according to the present invention. A vertical sectional view showing a second embodiment of the harmful light blocking device, FIGS. 4 and 5 are explanatory diagrams of the main parts of FIG. 3, respectively. 1... Lens barrel, 2... Front lens group, 3
... Rear lens group, 4 ... Zoom ring, 5 ... Frame, 6 ... Arm, 9.
...Aperture tool, 10...Cam groove, 11...
...Aperture, 12...Mount frame, 13...
... Rear cover 15 ... Cam groove, 17,1
8...long groove, 19...spring.

Claims (1)

[Claims] 1. In a zoom lens that has a front lens group and a rear lens group supported by a lens barrel, and is provided with an aperture that blocks harmful light behind the rear lens group, the aperture is moved in the optical axis direction of the lens. A harmful light blocking device for a zoom lens, characterized in that the diaphragm is connected to the rear lens group, and the diaphragm is moved following the movement of the rear lens group.