JPH0915476A - Zoom lens barrel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens barrel equipped with a flare preventing device capable of cutting a harmful luminous flux in accordance with respective focal lengths without increasing the thickness of a camera. SOLUTION: As for a lens frame 2 held by a frame 4 out of the lens groups 1 and 2; the frame 4 is extended to a specified position according to a zooming position by a driving member so as to change the focal length. A rotary moving barrel 8, straight advance bodies 9 and 10, and a rotary moving barrel 12 are attached to a fixed barrel 7 holding the entire lens barrel, and a flare preventing barrel 13 is attached to the inside of the moving barrel 12 so that it may straight advance and move according to the zooming position. The preventing barrel 13 is fitted in a cam 12a. A straight advance moving barrel 6 and the preventing barrel 13 are fitted and the preventing barrel 13 is moved back and forth by regulating the rotation of the moving barrel 12 and the straight advance of the moving barrel 6. The inner wall of the preventing barrel 13 is painted to prevent the harmful reflected light 16 from being reflected in a lens direction or formed to prevent the reflected light from being made incident.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable-focus zoom lens barrel having a flare prevention device that produces an effective hood effect according to the focal length, and more particularly to a zoom lens barrel at the time of variable focus. The present invention relates to a zoom lens barrel equipped with a device that exhibits a flare prevention effect according to the movement of the lens.

[0002]

2. Description of the Related Art As a flare prevention device proposed in a conventional variable focus camera, a mechanism for holding a flare prevention plate between a lens and an aperture to reduce flare is known. Such techniques include, for example, JP-A-6-201166, JP-A-6-289473, and Japanese Patent Application No. 2-254849.

[0003]

However, in recent years, a camera of this type has been made thinner, and in the above-mentioned conventional technique, a flare prevention mechanism is provided between the lens and the aperture.
There is a drawback that the thickness of the camera (thickness of the lens barrel: the dimension in the optical axis direction) increases.

The present invention has been made in view of such conventional problems, and a zoom equipped with a flare prevention device capable of cutting harmful light flux according to each focal length without increasing the thickness of the camera. An object is to provide a lens barrel.

[0005]

A zoom lens barrel according to claim 1 of the present invention has a plurality of barrels movable in the optical axis direction and a frame for holding a lens group in the barrels. In the zoom lens barrel that changes the focal length of the lens group by moving the barrel, a flare prevention barrel that is movable in the optical axis direction with the movement of the plurality of barrels is provided.

The zoom lens barrel according to claim 2 is
The inner surface of the flare prevention cylinder is characterized in that harmful light that hits the inner surface is reflected toward the object side and is not incident on the lens.

Further, the zoom lens barrel according to claim 3 is characterized in that an antireflection coating is applied to the inside of the flare prevention tube.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a zoom lens barrel according to the present invention will be described below with reference to the drawings. 1 is a sectional view showing a telephoto state and FIG. 2 is a wide-angle state.

The lens groups 1 and 2 that move in the optical axis direction and change the focal length depending on their respective positions are held by the frames 3 and 4, respectively. The frame 3 is held by a main plate 5 that holds a shutter, and the frame 3 and the main plate 5 are held by a straight-moving cylinder 6. The frame 4 that holds the lens group 2 is extended to a predetermined position according to the zoom position by a driving member (not shown).

A fixed barrel 7 for holding the entire lens barrel is provided with one or more straight-moving keys 7a on the inner diameter side, and a helicoid 7b on the inner circumference. On the other hand, the rotary moving cylinder 8 fitted to the inner circumference of the fixed cylinder 7 has a straight-moving key 7 of the fixed cylinder 7 on the outer peripheral side.
There is provided a helicoid 8b into which b is fitted. Further, a gear (not shown) is provided on the outer peripheral side, and the rotation of the gear and the lens barrel drive gear (not shown) and the helicoids 7b and 8b cause the rotary moving barrel 8 to move back and forth in the optical axis direction while rotating. ing.

A rectilinear body 9 is fitted in the rectilinear key 7a of the fixed cylinder 7, and the rectilinear body 9 sandwiches the rotary moving cylinder 8 so that the rectilinear body 1
It is fixed with 0 and screw 11. The rectilinear body 10 is fitted in the rectilinear moving cylinder 6.

A cam 8a is provided on the inner periphery of the rotary moving barrel 8 which moves back and forth while rotating, and which moves the straight moving barrel 6 straight by the rotation of the rotary moving barrel 8. A pin 6a held by the straight-moving barrel 6 is fitted to the cam 8a, and the straight-moving barrel 6 moves straight by rotation of the rotary moving barrel 8 and restriction of the straight-moving body 9.

In addition to the cam 8a, the rotary moving barrel 8 is provided with a rotary cam 8c on the inner peripheral side, which fits into the boss of the rotary moving barrel 12. Further, of course, since the pin 6a has an escape portion in the rotation direction, the movement of the rotation moving barrel 12 and the rectilinear movement barrel 6 in the optical axis direction is the same, and the rotation movement barrel 12 rotates in the direction of the rotation movement barrel 8 Due to the restriction of the straight movement of the movable barrel 6, the movable barrel 6 rotates in the optical axis direction while moving in the same manner as the straight movable barrel 6.

A flare prevention cylinder 1 is provided inside the rotary moving cylinder 12.
It has a cam 12a for letting out 3 while moving straight ahead by a predetermined length 1 depending on the zoom position. The cam 12a is fitted to the boss of the flare prevention tube 13. Further, the straight moving cylinder 6 and the flare prevention cylinder 13 are also fitted together, and the rotary moving cylinder 12
Due to the rotation of and the straight-movement restriction of the straight-moving cylinder 6, the flare prevention cylinder 13 moves straight forward and backward.

The inner wall of the flare prevention tube 13 has the harmful reflected light 1
6 is coated to prevent it from being reflected in the lens direction, or has a shape that does not allow reflected light to enter (for example, a cross-sectional shape as shown in FIG. 3: the arrow in FIG. 3 indicates the direction of the film surface). .

The entire zoom lens barrel described above is
The zoom lens barrel is fixed on a camera body (not shown) having the aperture 14 and covered with a cover 15. The zoom lens barrel is housed on the same surface as the cover 15 in the collapsed state although not shown.

[0017]

As described above, in the zoom lens barrel according to the first aspect of the present invention, the flare prevention tube is installed in a place other than between the lens and the aperture, and the flare prevention tube moves in the optical axis direction along with the zooming movement. Therefore, there is an effect that harmful light flux can be cut according to each focal length without increasing the thickness of the camera.

As described above, in the zoom lens barrel according to the second aspect of the present invention, the flare prevention cylinder has an inner surface shape that reflects harmful light to the object side and does not enter the lens. There is an effect that the light reflected on the inner wall surface of the cylinder is prevented from entering the lens, and the flare prevention effect can be further enhanced.

As described above, in the zoom lens barrel according to the third aspect of the present invention, the anti-reflection coating is applied to the inside of the flare prevention cylinder so that the light reflected by the inner wall surface of the cylinder for flare prevention enters the lens. There is an effect that it becomes possible to further improve the effect of preventing flare.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a telephoto state of an embodiment of a zoom lens barrel according to the present invention.

FIG. 2 is a sectional view showing the same wide-angle state.

FIG. 3 is a sectional view showing an example of a sectional shape of an inner wall of a flare prevention cylinder.

[Explanation of symbols]

 1 and 2 lens groups 3 and 4 frame 5 base plate 6 straight moving cylinder 6a pin 7 fixed cylinder 7a straight moving key 7b helicoid 8 rotary moving cylinder 8a cam 8b helicoid 8c rotating cam 9 straight moving body 10 straight moving body 11 screw 12 rotary moving barrel 12a cam 13 Flare prevention tube 14 Aperture 15 Cover 16 Harmful reflected light

Claims (3)

[Claims] 1. A zoom lens barrel having a plurality of barrels movable in the optical axis direction and a frame for holding a lens group in the barrels, wherein the focal length of the lens group can be varied by the movement of the barrels. A zoom lens barrel, characterized in that a flare prevention barrel is provided that is movable in the optical axis direction as the plurality of barrels move. 2. The zoom lens barrel according to claim 1, wherein the flare prevention cylinder has an inner surface shape that reflects harmful light hitting the inner surface toward the object side and does not enter the lens. 3. The zoom lens barrel according to claim 1, wherein an antireflection coating is applied to the inside of the flare prevention tube.