Lens barrier opening/closing device of a movable lens barrel

Abstract

A lens barrier opening / closing device of a movable lens barrel includes a barrier blade which is driven to open and close a photographic aperture; a barrier drive ring driven to rotate about an optical axis; a first biasing device which biases the barrier drive ring in a rotational direction; a rotational barrel which rotates about the optical axis; a receiving surface formed on the barrier drive ring to extend parallel to the optical axis; and a transmission surface, formed on the rotational barrel, extending parallel to the optical axis. The receiving surface and the transmission surface are engaged with each other to rotate the barrier drive ring together with the rotational barrel about the optical axis in a direction against a biasing force of the first biasing device when the movable lens barrel moves from either the photographing position to the accommodation position or vise versa.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a lens barrier opening / closing device for opening and closing a lens barrier which is disposed in a front end of a movable lens barrel for the purpose of preventing the front surface of the lens from being stained or damaged.[0003]2. Description of the Related Art[0004]A zoom lens of a camera which has a movable barrel driven to advance from a housed position (accommodation position) to a photographing position when the power is turned ON is known in the art. Such a zoom lens which is provided in the front end thereof with a lens barrier (which generally has a plurality of movable barrier blades) that is driven to open and close a forefront photographic aperture of the zoom lens by moving the movable barrel of the zoom lens from the housed position to the advance position and from the advance position to the housed position, in that order, is also known in the art.[0005]In one of the len...

AI Technical Summary

Benefits of technology

[0010]The present invention has been devised in view of the matters mentioned above, and accordingly, an object of the present invention is to provide a lens barrier opening / closing device with which the lens barrier operates with reliability without deteriorating the operational performance of the movable lens barrel.

Problems solved by technology

However, the performance of the advancing / retreating operation of the movable barrel of the zoom lens, which moves between the housed position and the photographing position, deteriorates if the spring force is excessively large.

However, according to this structure, such an operation of converting a driving force in the direction of the optical axis into a rotational driving force about the optical axis results in a large energy loss.

Accordingly, although the spring (biasing device) that biases the barrier blades preferably has a large spring force to reliably open and close as mentioned above, the performance of the advancing / retreating operation of the movable barrel of the zoom lens may deteriorate due to the large spring force since energy loss in an operation of transmitting a driving force from the linear movable member to the barrier drive is large.

If the driving force for moving the movable barrel in the direction of the optical axis is increased to prevent this from occurring, an excessive load is exerted on a drive motor which drives the movable barrel.

There is further problem in such lens barrier opening / closing devices in which the barrier blades are opened and closed by rotation of the barrier drive ring.

Namely, the lens barrier may not function properly if the rotational center of the barrier drive ring is eccentric from a predetermined position (generally the optical axis of the photographic optical system of the zoom lens).

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