JP2002202451A - Light shielding mask for lens barrel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light shielding mask for a lens barrel, which lowers a ghost phenomenon and a flare phenomenon with a simple construction. SOLUTION: The light shielding mask 21 fitted at the final part of a first straight advance limiting member 2 for limiting advance is provided with a projected part 21A which projects toward the lens side on the peripheral face of an aperture part 21B of the light shielding mask 21. Despite that the whole outer peripheral face of the aperture part 21B projects to the lens side, it is sufficient that two sides of the aperture part are light-shielded when the shorter sides of a imaging plane are light-shielded, and the form of the projected part is not limited to the one shown in Fig. 1 (b).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-shielding mask, and more particularly, to a light-shielding mask used for an optical device such as a camera.

[0002]

2. Description of the Related Art Conventionally, there has been provided a so-called zoom lens which can change a photographing angle of view by changing a lens focal length of a photographing lens group provided in a camera to photograph at an arbitrary photographing angle of view. Cameras are common. Cameras equipped with these zoom lenses move the shooting lens between a non-shooting state (camera collapsed state), a state with the shortest focal length (wide state of the camera), and a state with the longest focal length (tele state of the camera). 2. Description of the Related Art A lens barrel is provided as a mechanism capable of moving a photographing lens group in a photographing optical axis direction.

In recent years, the demand for miniaturization of a zoom camera has resulted in a lens barrel attached to the zoom camera being a multi-stage lens barrel, and the demand for higher magnification has increased the back focus of the zoom lens. A lens barrel is needed.

For this reason, light other than the effective luminous flux necessary for exposing the photographing screen to the inside of the lens barrel particularly in the telephoto state of the camera enters the inside of the lens barrel through the lens opening, and the inside of the lens barrel is opened. A so-called ghost phenomenon or a flare phenomenon that easily reaches the film after being reflected by the member is likely to occur (detailed in the embodiment of the invention). Since the ghost phenomenon and the flare phenomenon deteriorate the finish of a photograph, it is necessary for the lens barrel to prevent the ghost phenomenon and the flare phenomenon.

In order to prevent the reflection inside the lens barrel, there are various measures such as providing an antireflection member, and making the reflection surface of the barrel that reflects harmful light into a non-reflective shape. Since this also leads to an increase in the size of the lens barrel, it is necessary to take measures against the ghost phenomenon and the flare phenomenon that do not make the lens barrel large enough to meet the recent demand for downsizing of the camera.

[0006] Therefore, as a conventionally known technique, Japanese Utility Model Laid-Open No.
No. 107111 discloses a technology for preventing a ghost phenomenon by providing a light-shielding mask that allows an effective light beam to pass through an air space of a lens closer to a subject than a specific reflecting surface in an optical system including a plurality of lenses, but cuts a light beam outside the effective light beam. Is disclosed.

In Japanese Utility Model Application Laid-Open No. 2-107112, a light-shielding wall extending in the radial direction is provided on or near the final surface of the imaging optical system, and the center of the light-shielding wall is the most effective light beam passing through the final surface to form a screen. A technology has been disclosed in which an opening having a shape along the outside is formed to prevent a ghost phenomenon.

[0008]

However, in the configuration disclosed in Japanese Utility Model Laid-Open No. 2-107111, a ghost in the lens frame can be reduced since a light-shielding mask is provided at a lens air space on the object side of the specific reflection surface. In addition, it is impossible to reduce a ghost phenomenon caused by reflection of a lens barrel, particularly an internal member of the lens barrel having a long back focus of the lens.

In the configuration disclosed in Japanese Utility Model Application Laid-Open No. 2-107112, the ghost phenomenon from the final surface of the imaging optical system to the final surface can be reduced. Reflection at the member cannot be prevented.

Therefore, in the present invention, a ghost phenomenon and a flare phenomenon can be reduced with a simple structure by providing a light shielding portion projecting toward the lens at the opening of the effective light beam of the mask member attached to the lens barrel. An object of the present invention is to provide a cylindrical light-shielding mask.

[0011]

According to the first aspect of the present invention,
In a light shielding mask of a lens barrel having an imaging optical system,
The light-shielding mask is a light-shielding mask for a lens barrel, characterized in that at least one surface of an opening through which an effective light beam passes through the photographing screen projects toward the optical system.

According to this configuration, by providing the antireflection portion projecting toward the lens at the opening of the effective light beam of the mask member, reflection by the lens barrel member can be easily cut with a simple configuration.

According to a second aspect of the present invention, in the light-shielding mask for the lens barrel according to the first aspect, at least one surface of an opening through which an effective light beam with respect to a photographing screen passes is projected toward the optical system, and has a bent shape. A light-blocking mask for a lens barrel.

With this configuration, the ghost phenomenon and the flare phenomenon can be effectively reduced, and the light shielding mask is formed in a bent shape, so that it can be easily produced.

According to a third aspect of the present invention, there is provided the light-shielding mask for the lens barrel according to the first or second aspect, wherein the light-shielding mask is attached to a straight movement restricting member of the lens barrel.

According to this configuration, since the mask member is attached to the straight movement restricting member of the lens barrel member, the opening for the effective light flux does not become large. For this reason,
The lens barrel can be kept compact and the reflection by the lens barrel member can be easily cut with a simple configuration.

According to a fourth aspect of the present invention, there is provided a light shielding mask for a lens barrel, wherein the light shielding mask has an anti-reflection color.

According to this configuration, since the mask member has an anti-reflection color, the mask member does not reflect.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) The present invention will be described with reference to an embodiment.

A first embodiment of the present invention will be described. Since the technology of the camera body and the like is a known technology, a detailed description is omitted here. In addition, the lens support frame and the shutter mechanism provided in the lens barrel are well-known technologies, and detailed description thereof will be omitted.

FIG. 2 is an exploded perspective view of a lens barrel to which the present invention is applied. The lens barrel includes a fixed barrel 1 and a three-stage advance / retreat barrel capable of moving back and forth with respect to the fixed barrel 1 in the optical axis direction. It is composed of groups. The three-stage reciprocating cylinder group includes a foremost reciprocating cylinder 6, a next-stage second-stage advancing / retracting cylinder, and a next-stage, first-stage advancing / retreating cylinder preceding the fixed cylinder (last-stage advancing / retreating cylinder) It is composed of

The frontmost reciprocating cylinder 6 advances and retreats in the optical axis direction without rotating around the optical axis.

The first-stage advance / retreat cylinder is disposed inside a first-stage rotary cylinder member 3 that advances and retreats in the optical axis direction while rotating around the optical axis, and radially inside the first-stage rotary cylinder member 3. It comprises a first-stage rotating cylinder member 3 and a first-stage rectilinear regulating member 2 which advances and retreats in the optical axis direction integrally without rotating around the optical axis.
The first-stage rotating cylinder member 3 and the first-stage rectilinear regulating member 2 can be integrally advanced and retracted parallel to the photographing optical axis direction by a bayonet connection (not shown).

The second-stage advance / retreat cylinder is disposed inside a second-stage rotary cylinder member 5 that advances and retreats in the optical axis direction while rotating around the optical axis, and radially inside the second-stage rotary cylinder member 5. It comprises a second-stage rotary cylinder member 5 and a second-stage rectilinear member 4 which advances and retreats in the optical axis direction integrally without rotating around the optical axis. Second
The step rotating member 5 and the second step linear member 4 can integrally move in parallel to the photographing optical axis direction by bayonet coupling (not shown).

On the outer surface of the first-stage rotary cylinder member 3, a gear portion 3A to which rotational driving force from a gear train driven by a zoom motor (not shown) is transmitted, and a helicoid screw formed on the inner surface of the fixed cylinder. A helicoid screw portion 3B (female screw) that engages with the portion 1A (male screw) is formed. On the outer periphery of the first-stage rectilinear regulating member 2, a convex rectilinear guide engaging portion 2 </ b> A that engages with a concave rectilinear guide engaging portion 1 </ b> B formed on the inner surface of the fixed cylinder 1 is formed.

When the first-stage rotary cylinder member is rotationally driven by a gear train from a zoom motor, the helicoid screw portion 1 is rotated.
Due to the helicoid engagement action between A and 3B, it is driven straight ahead in the optical axis direction while rotating around the optical axis. When the first-stage rotary cylinder member 3 rotates around the optical axis, the first-stage straight movement restricting member 2
Is linearly guided in the optical axis direction by the linear guide engagement portion 1B, and is driven linearly in the optical axis direction integrally with the first-stage rotary cylinder member 3.

A pin 4A is formed on an outer surface of the second-stage linear member 4. The pin 4A is engaged with a cam groove 3C formed on an inner surface of the first-stage rotary cylinder member 3, and is provided with a first pin.
It is formed on the inner diameter side of the step linear movement restricting member 2, extends in the optical axis direction, and is engaged with a linear guide engagement portion 2 </ b> B arranged radially inside the frontmost retractable cylinder 6. First stage rotary cylinder member 1
When the rotary member 4 rotates about the optical axis, the second-stage linear member 17 is guided linearly in the optical axis direction by the linear guide engagement portion 4B, and the cam pin 3C engages with the pin 4A in the optical axis direction. Is driven straight ahead.

On the outer surface of the second-stage rotary cylinder member 5, a groove 3 formed on the inner surface of the first-stage rotary cylinder member 14 and parallel to the optical axis direction is formed.
A pin 5A engaging with D is formed. When the first-stage rotary cylinder member 3 rotates around the optical axis, the second-stage rotary cylinder member 5
Is rotated integrally with the first-stage rotary cylinder member 3 by the engagement action between the groove 3D and the pin 5A, and is rotated by the cam pin engagement between the second-stage linear member 4 and the first-stage rotary cylinder member 3. It is linearly driven integrally with the linear member 4 in the optical axis direction.

The frontmost reciprocating cylinder 6 is sandwiched in the radial direction by the second-stage rotary cylinder member 5 and the second rectilinear member 4 at the next subsequent stage. That is, the second-stage rectilinear member 4 is disposed radially inward of the forward-backward reciprocating cylinder 6.

A helicoid portion 6A is formed on the outer surface of the frontmost reciprocating cylinder 6 so as to engage with a helicoid screw (not shown) formed on the inner surface of the second-stage rotary cylinder member 5. on the other hand,
On the inner surface of the frontmost reciprocating cylinder 16, a concave rectilinear guide engaging portion that engages with a convex rectilinear guide engaging portion 4 </ b> B formed on the outer surface of the second rectilinear cylindrical member 17 and extending in the optical axis direction. (Not shown) are formed. As a result, the frontmost reciprocating cylinder 6
When the second-stage rotary cylinder member 5 rotates around the optical axis,
While being guided in the optical axis direction by the rectilinear cylinder member 4, it is driven in the optical axis direction.

Although the structure and the driving mechanism of the lens barrel have been described above, the lens barrel driving is a known technique, and a detailed description thereof will be omitted.

FIG. 1 shows an antireflection member according to the present embodiment. FIG. 1A is an overall view of the first-stage rectilinear regulating member 2, and FIG. 1B is a light-shielding mask 21 of the present invention attached to the last portion of the first-stage rectilinear regulating member 2. FIG. 1 (b)
As shown in the figure, a projection 21A protruding toward the lens is provided on the outer peripheral surface of the opening 21B of the light-shielding mask. The figure protruding toward the lens is shown in FIG. Also, in FIG. 1B, the entire outer periphery of the opening 21B protrudes toward the lens. For example, when only the short side of the photographing screen is shielded, the two sides of the opening may be shielded. Fig. 1
It is not limited to (b).

FIG. 3 shows a state where the focal length is longest in the lens barrel according to the present embodiment, and FIG. 4 is an enlarged view of the reflecting portion circled in FIG. Reference numeral 7 denotes a second group lens, and reference numeral 8 denotes a first group lens. Reference numeral 9 denotes an effective luminous flux constituting a shooting screen;
Denotes a light beam outside the shooting screen, and 11 denotes an optical film.

FIG. 6 shows a conventional example for easy explanation. As can be seen from FIG. 6, light 1 entering from outside the effective light flux
0 is reflected by the first-stage straight movement regulating member 2 and the optical film 1
1 and a ghost phenomenon has occurred.

In this embodiment, as shown in FIG. 3, the light beam 10 entering from outside the effective light beam enters the reflecting portion in the X direction as shown in FIG. 4, and is reflected by the first-stage straight movement restricting member 2. The reflected light is further projected to the projection 21A of the light shielding mask 21.
Is reflected in the lens direction Y in FIG. With this configuration, the reflected light does not reach the film surface, so that the ghost phenomenon can be reduced.

Further, the reflection can be further reduced by making the light-shielding mask an anti-reflection color, for example, black.

The light-shielding mask of this embodiment is similar to that of FIG.
As shown in (b), since the aperture is formed in the shape of a stop, the same effect can be obtained over the entire circumference of the opening of the member of the light shielding mask. In addition, since effective light shielding can be performed by one component, it is possible to prevent unnecessary cost increase of the lens barrel and the camera. Further, the light-shielding mask according to the present embodiment is made of a material capable of forming an aperture shape.
Since the material capable of forming the aperture shape can be formed of a very thin material, it is possible to prevent reflection without increasing the thickness of the camera in the optical axis direction more than necessary.

The present invention is preferably attached to a straight movement restricting member as in this embodiment. If it is mounted on a rotating member, the range of the effective light beam changes depending on the zoom position, and as a result, a circular effective light beam range is required. This reduces the light-shielding performance of the light-shielding mask at the same time as the size of the opening increases. Therefore, this embodiment is desirable.

The present invention is not limited to the embodiment.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIG. Since the operation of the lens barrel is the same as that of the first embodiment, a detailed description is omitted here. In addition, the operation of the camera is a well-known technique, and thus a detailed description is omitted here.

As shown in FIG. 5B, in the light-shielding mask of the present embodiment, the light-shielding portion 22A is formed in a bent shape so as to project toward the lens with respect to the opening 22B. FIG.
(A) shows the entire first-stage straight traveling regulating member. Since the opening 22B of the first-stage rectilinear regulating member 2 is arranged closest to the film surface in the present embodiment, the opening 22B has a rectangular shape according to the photographic film. At this time, in order to reduce the size of the lens barrel, the diameter of the barrel in the direction c and the opening 22 are required.
Since the distance between B and B is also small, the distance between the effective luminous flux and the first-stage straight movement restricting member 2 in the direction c is small. When the distance between the effective light flux and the lens barrel becomes small, a ghost phenomenon is likely to occur. On the other hand, in the direction d, the diameter of the lens barrel and the distance from the opening 22B are larger than the direction c.

Therefore, as in the present embodiment, a sufficient distance is provided in the d direction so as not to cause reflection without a light shielding portion,
By employing a configuration in which the light shielding portion is provided only in the direction c, the ghost phenomenon and the flare phenomenon can be effectively reduced. In addition, since the light-shielding mask is formed in a bent shape, it can be easily manufactured.

In this embodiment, the light shielding portion is provided only in the direction c, but the light shielding portion may be provided on all four sides.

The present invention is not limited to the light-shielding mask of the lens barrel of the camera according to the present embodiment, but can be applied to any light-shielding mask of a lens of an optical device.

[0045]

According to the first aspect of the present invention, the antireflection portion projecting toward the lens is provided at the opening of the effective light beam of the mask member, so that the reflection by the lens barrel member can be easily cut with a simple configuration. Can be.

According to the second aspect of the present invention, since the mask member is attached to the straight movement restricting member of the lens barrel member,
The opening for the effective light beam is not enlarged. For this reason, since the lens barrel does not need to be enlarged, the reflection by the lens barrel member can be easily cut with a simple structure while keeping the lens barrel compact.

According to the third aspect of the present invention, since the mask member has an anti-reflection color, the mask member does not reflect. That is, a ghost phenomenon and a flare phenomenon can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is a developed perspective view of the lens barrel of the present invention.

FIG. 3 is a diagram illustrating an effect of the first exemplary embodiment of the present invention.

FIG. 4 is an enlarged view of FIG. 3;

FIG. 5 is a diagram of a second embodiment of the present invention.

FIG. 6 is a diagram showing a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fixed cylinder 1A Helicoid screw in fixed cylinder 1B Straight guide of first-stage straight movement regulating member in fixed cylinder 2 First-stage straight movement regulating member 2A Straight guide engaged with fixed cylinder 2B Straight guide of second-stage straight movement member 3 First Step rotating cylinder member 3A Gear portion of first stage rotating cylinder member 3B Helicoid screw portion engaging with fixed cylinder of first stage rotating cylinder member 3C Driving cam of second stage linear member 3D Rotation groove of second stage rotating cylinder member 4 Second-stage linear member 4A Cam pin of the second-stage linear member 4B Straight-line guide engaging portion of the foremost-stage linear member in the second-stage linear member 5 Second-stage rotary cylinder member 5A First in the second-stage rotary cylinder member Engagement pin with step rotating cylinder member 6 Foremost advance / retreat cylinder 6A Helicoid screw of foremost advance / retreat cylinder 7 2nd lens 8 1st lens 9 Effective light flux 10 Effective light flux 11 Optical film 21 Light-shielding mask according to the first embodiment 21A First Light-shielding portion 21B of light-shielding mask of embodiment 21B Opening of light-shielding mask of first embodiment 22 Light-shielding mask of second embodiment 22A Light-shielding portion of light-shielding mask of second embodiment 22B Second embodiment Of light-shielding mask in the form of

Claims (4)

[Claims] 1. A light-blocking mask for a lens barrel having a photographing optical system, wherein the light-blocking mask has at least one surface of an opening through which an effective light beam passes through a photographing screen, protruding toward the optical system. Shading mask. 2. The light-shielding mask for a lens barrel according to claim 1, wherein at least one surface of an opening through which an effective light beam passes to the photographing screen projects toward the optical system and has a bent shape. A light shielding mask for the lens barrel. 3. The light-shielding mask for a lens barrel according to claim 1, wherein the light-shielding mask is attached to a straight movement restricting member of the lens barrel. 4. A light shielding mask for a lens barrel, wherein the light shielding mask has an anti-reflection color.