Driving mechanism for a photographic lens

#1. Field of the Invention

#The present invention relates to a driving mechanism for a photographic lens adapted to move the photographic lens back and forth in parallel to an optical axis for power varying or focusing.

#2. Description of the Related Art

#In the drawings:

#FIG. 1 is a sectional view taken along a plane including an optical axis S, showing an optical system incorporated with a driving mechanism of the invention as a photographic lens having been moved to its foremost position for effective photographing;

#FIG. 2 is a view similar to FIG. 1 showing the same optical system but as the photographic lens having been moved to its rearmost position for effective photographing;

#Details of the inventive driving mechanism for a photographic lens will be more fully understood from the description of a preferred embodiment given hereunder in reference with the accompanying drawings. While the invention will be described hereunder specifically with respect to the case in which this driving mechanism is used to drive a zoom lens system of a built-in type, it should be understood that the driving mechanism of the invention can be used also to drive a zoom lens system of an interchangeable type. The zoom lens system of built-in type can be conveniently driven by using an electric motor as will be described. For the zoom lens system of interchangeable type, on the other hand, it is also possible to achieve a desired zooming effect manually, instead of using the electric motor.

#FIGS. 1 and 2 are sectional views taken along the plane including the optical axis S, respectively showing the optical system provided with the driving mechanism of the present invention with the photographic lens having been moved to its foremost and rearmost positions for effective photographing. It should be understood that, if desired, there additionally may be provided a mechanism by which the photographic lens can be further retracted relative to the position shown in FIG. 2 until a lens barrel assembly substantially sinks in a camera body 1. FIGS. 3-5 are exploded perspective views, respectively showing the important components of the driving mechanism. A stationary lens barrel 2 provided integrally with the camera body 1 telescopically receives therein a first driving lens barrel 11. A female helicoid 2a formed in inner peripheral surface of the stationary lens barrel 2 is operatively associated with a male helicoid 11b formed on outer peripheral surface of the first driving lens barrel 11 in the proximity of its rear end. Thus, rotation of the first driving lens barrel 11 around the optical axis S relative to the stationary lens barrel 2 causes said first driving lens barrel 11 to be moved back and forth relative to stationary lens barrel 2 in parallel to the optical axis S at a predetermined rate of movement. It should be understood that a rear portion of the stationary lens barrel 2 is not shown in detail to avoid a complexity of illustration.

#First driving lens barrel 11 telescopically receives therein a second driving lens barrel 12. A female helicoid 11a formed in inner peripheral surface of the first driving lens barrel 11 is operatively associated with a male helicoid 12b formed on outer peripheral surface of second driving lens barrel 12 in the vicinity of its rear end. Thus, rotation of this second driving lens barrel 12 around the optical axis S relative to the first driving lens barrel 11 causes second driving lens barrel 12 to be moved back and forth relative to first driving lens barrel 11 along the optical axis S at a predetermined rate of movement. Second driving lens barrel 12, in turn, telescopically receives therein a movable lens barrel 13. A female helicoid 12a formed in inner peripheral surface of the second driving lens barrel 12 is operatively associated with a male helicoid 13b. In this manner, rotation of second driving lens barrel 12 around the optical axis S causes movable lens barrel 13 to be moved back and forth in parallel to the optical axis S relative to second driving lens barrel 12 at a predetermined rate of movement.