JPH03107132A - Aperture opening regulator of zoom lens - Google Patents

Abstract

PURPOSE:To maintain the aperture opening diameter always at an adequate value according to focal distances and to increase the degree of freedom of design by regulating the turning range of the driving lever of a shutter by a cam face, thereby adjusting the shutter opening diameter. CONSTITUTION:This device is constituted by having the driving lever 30 which drives the opening and closing of shutter vanes 28a, 28b of the program shutter 28 by turning and varies the opening diameter of the shutter vanes in correspondence to the driving range thereof and the cam 32 which is formed with inclination to the optical axis in a lens barrel and regulates the turning range of the lever 30 according to the focal distance by coming into contact with a part of the lever 30 at the time of opening of the shutter vanes. A part of the lever 30 comes into contact with the cam surface 32 formed according to the focal distance when the lever 30 turns to open the shutter 28 at the time of photographing. The driving range of the lever 30 is regulated and the aperture opening diameter of the shutter 28 is set at the adequate value corresponding to the focal distance of the zoom lens.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an aperture aperture regulating device for a zoom lens that regulates the maximum aperture diameter of a shutter blade incorporated in a lens group that moves during zooming. .

[Conventional technology °]

Zoom lenses have been used as photographic lenses in recent compact cameras. Two-group or three-group compact zoom lens systems are used as zoom lenses for compact cameras, but these zoom lenses have an aperture in the lens group that moves in the optical axis direction during zooming. Therefore, if a program shutter that also serves as an aperture is used as a shutter, the shutter blades must also be incorporated into the movable lens group.

By the way, generally when you change the focal length of a zoom lens, the F-number of the lens changes and you need to adjust the aperture aperture, but with recent zoom lenses that have a built-in program shutter, By optically correcting the movement of the lens group and electrically adjusting the opening/closing time of the shutter blades, we have succeeded in maintaining the maximum aperture of the shutter blades (corresponding to the aperture diameter) constant regardless of the focal length. has been done.

[Problem to be solved by the invention]

However, when the maximum aperture of the shutter blade is maintained constant for the same subject brightness, whether during telephoto shooting or wide-angle shooting, there will be a large difference in the optical performance of the lens. In other words, when taking wide-angle shots, rays with large deviations from the optical axis also contribute to image formation, which results in aggravation of various aberrations compared to when taking telephoto shots, which deteriorates image quality. be. If this problem were to be solved by optical design, it would be necessary to increase the number of lenses and increase the aperture of the lenses, making it extremely difficult to achieve the low cost and compactness required for zoom lenses for compact cameras.

[Purpose of the invention]

The present invention has been made in view of this point, and by setting the aperture aperture diameter to an appropriate value according to the focal length,
It is an object of the present invention to provide a diaphragm aperture regulating device that can increase the degree of freedom in lens design.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a drive lever that rotates to drive the shutter blades of a program shutter to open and close, and that changes the aperture diameter of the shutter blades in accordance with the range of rotation, and a lens barrel. The lens is provided with a cam that is inclined in the optical axis direction, contacts a part of the drive lever when the shutter blade is opened, and regulates the rotation range of the drive lever according to the focal length.

[Effect]

Since the present invention is configured as described above, when the drive lever rotates and the shutter opens in the ↑ liquid type, a part of the drive lever comes into contact with a cam surface formed in accordance with the focal length. This restricts the drive range of the drive lever,
The aperture diameter of the shutter is set to an appropriate value according to the focal length of the zoom lens.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows the internal structure of a zoom lens incorporating an aperture regulating device according to the present invention.

This zoom lens has a cam barrel 10. Fixed cylinder 11
．． The triple tube of the movable tube 12 and the first group lens 14 arranged inside the movable tube 12. Second group lens 16. It is composed of a third group lens 18.

The cam barrel lO is rotatably supported by the camera body,
A cam groove 10a through which a guide pin 13 fixed to the movable barrel 12 is inserted, and a movable frame 16a that supports the second group lens 16.
A cam groove 10b through which a guide pin 16b fixed to the cam groove 10b is inserted.
and a guide groove into which a guide pin (not shown) fixed to the third group lens 18 is inserted is formed.

The fixed barrel 11 is fixed to the camera body, and has linear guide grooves 11a and llb parallel to the optical axis that guide the guide pins 13 and 16a, respectively.

The movable barrel 12 moves in the optical axis direction as the cam barrel 10 rotates during a zooming operation.

The first lens group 14 is fixed to the movable barrel 12 and moves in the optical axis direction along with the movable barrel 12 by a zooming operation.

The second group lens 16 and the third group lens 18 are moved by the guide bars 22 and 23, respectively, by the movement of the guide pins described above.
along the optical axis. This corrects the movement of the focal plane and aberrations caused by zooming.

Among the lenses constituting the second lens group 16, the lens 16a placed at the front moves in the optical axis direction to perform focusing. Further, a shutter device is provided within the second group lens 16, and after focusing, the shutter blade 28 is driven to open and close by a drive lever 30.

A cam surface 32 that comes into contact with the tip of the drive lever 30 is formed below the drive lever 30 . This cam surface 32 is inclined so that the rear side is lower, and the second group lens 1
When the lens 6 moves forward with respect to the movable barrel 12, it contacts the drive lever 30 at a high position, and when the second group lens 16 moves rearward, it contacts the drive lever 30 at a low position. In other words, as the shooting becomes wider, the lens comes into contact with the drive lever 30 at a higher position.

FIG. 2 shows the configuration of the drive mechanism for the shutter blade 28. As shown in FIG. Note that this figure corresponds to FIG. 1 and shows the state at the time of wide-angle photography.

The shutter blade 28 consists of a first blade 28a and a second blade 28b, each of which rotates around a pin 36. Elongated holes 37 and 38 are formed in these shutter blades 28a and 28b, respectively, for connection to the drive lever 30 by pins 33 and 35.

The drive lever 30 opens and closes the shutter blades 28a and 28b, and is connected to a portion of the outer periphery of a pulse motor 40 by a pin 42, and rotates about a pin 44 when the pulse motor 40 is driven. Due to such rotation, the shutter blades 28a and 28b each rotate about the pin 36, thereby opening and closing the optical path. That is, when opening the optical path, the pulse motor 40 rotates clockwise, and the drive lever 30 also rotates clockwise.

Conversely, when closing the optical path, the drive lever 30 is rotated counterclockwise by the counterclockwise rotation of the pulse motor 40.

The tip 30a of the drive lever 30 is formed into a smooth arc shape, and comes into contact with the cam surface 32 when the drive lever 30 rotates toward the opening side (counterclockwise), and the drive lever 30, that is, the opening diameter by the shutter blade 28a and the shutter blade 28a is regulated. Note that reference numeral 30b is a balancer provided at the opposite end of 30a, and contributes to smooth rotation of the drive lever 30.

Next, the operation and effect of the embodiment configured as above will be explained.

When performing wide-angle photography, the movable barrel 12 is located at the rearmost position as shown in FIG. When the movable barrel 12 moves rearward, the second group lens 16 moves forward within the movable barrel 12, and the drive lever 30 is located at the left end of the cam surface 32, that is, above the highest position. On the other hand, the third group lens 18 moves rearward.

This corrects the movement of the focal plane and aberrations. At this time, the shutter blades 28a and 28b maintain a closed state as shown in FIG.

Next, when the shutter button (not shown) is pressed halfway, the lens 16a of the second lens group 16 moves to perform focusing. When the shutter button is pressed even harder, the drive lever 3 is rotated by the rotation of the pulse motor 40.
0 rotated counterclockwise and the shutter blade 28a was in the state shown in FIG.

28b begin to rotate left and right, respectively. And the second
As shown in the figure, the tip 30a of the drive lever 30 comes into contact with the cam surface 32, and the rotation of the shutter blades 28a, 28b is temporarily stopped in a state where the diaphragm opening is considerably narrowed down. Therefore, light having a large angle of deviation that enters the lens is blocked, and the occurrence of aberrations can be kept to a minimum. Therefore, it is possible to take good pictures with little distortion.

After that, after opening the optical path for a predetermined time, the pulse motor 4
The clockwise rotation of 0 causes the drive lever 30 to rotate clockwise, and the shutter blades 28a28b are respectively rotated inward to close the optical path.

On the other hand, when performing telephoto shooting, the movable barrel 12 is extended toward the subject as shown in FIG. When the movable cylinder 12 moves,
The second group lens 16 moves rearward within the movable cylinder 12, and the drive lever 30 of the shutter blade 28 comes to be above the low position of the cam surface 32. Thereafter, after focusing as in the case of wide-angle photography, the pulse motor 40 is rotated to rotate the drive lever 30 counterclockwise.

When the drive lever 30 rotates counterclockwise, the fifth
As shown in the figure, the tip 30a of the drive lever 30 comes into contact with a low position of the cam surface 32, and the aperture by the shutter 28 is almost fully opened. Therefore, sufficient exposure can be obtained even though the angle of view is narrow. Thereafter, as in the case of wide-angle photography, the optical path is opened for a predetermined period of time and photography is performed.

〔Effect of the invention〕

As explained above, in the present invention, the aperture diameter of the shutter is adjusted by regulating the rotation range of the shutter drive lever by 4 degrees by the cam surface, so the aperture aperture diameter is always adjusted appropriately according to the focal length. This has the effect of increasing the degree of freedom in lens design.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of a zoom lens using an aperture regulating device according to an embodiment of the present invention. FIG. 2 is a front view showing the configuration of main parts of the embodiment. FIG. 3 is a front view showing the operation of the main parts of the embodiment. FIG. 4 is a sectional view showing the operation of the embodiment. FIG. 5 is a front view showing the operation of the main parts of the embodiment. 12...Moving tube 16...Second group lens 2nd...Shutter 30...Drive lever 32...Cam surface. Figure 2 Figure 3

Claims (1)

[Claims] (1) In a zoom lens in which a shutter blade that constitutes a program shutter that also serves as an aperture is incorporated into a lens group that moves in the optical axis direction within the lens barrel during zooming, the shutter blade is driven to open and close by rotating. a drive lever that changes the aperture diameter of the shutter blade in accordance with its rotation range; and a drive lever that is formed in the lens barrel with an inclination in the optical axis direction and that comes into contact with a part of the drive lever when the shutter blade is opened. A diaphragm aperture regulating device for a zoom lens, comprising a cam that is in contact with the drive lever and regulates the rotation range of the drive lever according to the focal length.